Method and device for reducing a communication device peak current

Abstract

Portable two-way radio (100), comprising: a transceiver (208) configured to process an audio signal representing a warning tone; a processor (204) coupled to the transceiver (208), the processor (204) configured to: Determining (405) whether the transceiver (208) is in a transmit state; and Determining (410) whether an audio volume level setting exceeds a threshold associated with an intensity of the alert tone; a current limit trigger circuit (214, 314) coupled to the processor (204); and a warning tone current limit controller (218, 318), wherein the current limit trigger circuit (214, 314) is configured to activate the warning tone current limit controller (218, 318) in response to determining (405) that the transceiver (208) is in the transmit state and determining (410) that the audio volume level setting exceeds the threshold associated with the intensity of the warning tone, the warning tone current limit controller (218, 318) comprising: a voltage scaling controller (368) configured to generate a reduced audio signal by adjusting a peak-to-peak amplitude of the audio signal representing the warning tone in response to activation by the current limiting trigger circuit (214, 314); and a warning tone amplitude modulator (372) configured to generate an adjusted audio signal by limiting the maximum amplitude of the reduced audio signal in response to activation by the current limiting trigger circuit (214, 314).

Description

BACKGROUND OF THE INVENTION

[0001] Many portable communication devices, such as two-way radios, are used to perform various types of communication. These types of communication, which can occur simultaneously in parallel, include standing wave radio transmission, LMR ("land mobile radio") transmission, LTE ("long-term evolution") transmission, and audible warning tone transmission. Portable communication devices can be battery-powered and can contain multiple components, including a transceiver and a processor.Each component of the portable communications device may consume power or draw current to operate, but the device may be limited in its power consumption or current consumption to satisfy compliance with one or more standards, including Appareils destinés à être utilisés en ATmosphères EXplosibles (ATEX), Underwriters Laboratories (UL), and International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres (IECEx).

[0002] For example, Division 1 compliance with UL standards may require a communications device to operate properly in environments containing concentrated levels of a flammable or combustible material, limiting the device's peak instantaneous current draw to maintain protection and safety. Peak instantaneous current draw may be required in a variety of scenarios in such environments. For example, protection and safety may be maintained through one or more communication signals based on audible warning tones. Current portable communications devices do not allow warning tones to be generated at desirable levels to maintain protection and safety without exceeding the power or current consumption requirements established by such standards.However, there are situations where it is not practical to reduce the volume of the warning tone or the perceived loudness of a warning tone to satisfy the power consumption limits or the power consumption limits. For example, in a situation where a user is working in an environment with concentrated levels of flammable or combustible material, as defined by the Division 1 UL standards, reductions in the volume of the warning tone or perceived loudness may hinder proper use of the portable communications device to maintain safety and security. In addition, some portable communications devices may achieve reductions in their power consumption or power consumption using techniques that do not satisfy requirements of other parts of the same standard or other compliance standards.A portable two-way radio with a power controller is already known from the prior art in the form of US 2002 / 0102952 A1, in which current limitation occurs depending on the transceiver's transmission state. Furthermore, a radio with a processor and a power controller is also already known from DE 10 2013 003 273 A1.

[0003] There is a limit to limiting power consumption or current consumption without violating other requirements associated with a compliance standard. This functionality typically cannot be achieved by simply reducing the warning tone volume or by adding an intermediate energy storage device, such as a capacitor, to amplify the warning tone output. BRIEF DESCRIPTION OF THE DIFFERENT VIEWS OF THE DRAWINGS

[0004] The accompanying figures, in which like reference numerals refer to identical or functionally similar elements throughout the several views, are incorporated in and constitute a part of the specification together with the following detailed description and serve to further illustrate embodiments of concepts incorporating the claimed invention and to explain various principles and advantages of such embodiments. Fig. 1A is a front perspective view of an exemplary portable communication device with peak instantaneous current reduction for warning tones, according to some embodiments. Fig. 1B is a rear perspective view of an exemplary portable communication device with peak instantaneous current reduction for warning tones, according to some embodiments. Fig. 2 is a block diagram illustrating an exemplary portable communication device with peak instantaneous current reduction for warning tones, according to some embodiments. Fig. 3 is a block diagram illustrating an exemplary warning tone current limit controller, according to some embodiments. Fig. 4 is a flowchart illustrating a method for peak instantaneous current reduction for warning tones, according to some embodiments. Fig. 5 is a flowchart illustrating a method for variable peak instantaneous current reduction for warning tones, according to some embodiments.

[0005] Those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help enhance understanding of embodiments of the present invention.

[0006] The system, method, and apparatus components have been represented by appropriate symbols in the drawings where appropriate, showing only those specific details essential to an understanding of the embodiments of the present invention, so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of this description. DETAILED DESCRIPTION OF THE INVENTION

[0007] Disclosed herein are systems, methods, and apparatus for reducing peak current of a communication device. In one embodiment, a disclosed portable two-way radio includes a transceiver, a processor coupled to the transceiver, a current limit trigger circuit coupled to the processor, and an alert tone current limit controller. The transceiver is configured to process an audio signal representing an alert tone. The processor is configured to determine whether the transceiver is in a transmit state and to determine whether an audio volume level setting exceeds a threshold associated with an intensity of the alert tone.The current limit trigger circuit is configured to activate the alert tone current limit controller in response to determining that the transceiver is in the transmit state and determining that the audio volume level setting exceeds the threshold associated with the intensity of the alert tone. The alert tone current limit controller may include a voltage scaling controller and a alert tone amplitude modulator. The voltage scaling controller is configured to generate a reduced audio signal by adjusting a peak-to-peak amplitude of the audio signal representing the alert tone in response to activation by the current limit trigger circuit, and the alert tone amplitude modulator is configured to generate an adjusted audio signal by limiting the maximum amplitude of the reduced audio signal in response to activation of the current limit trigger circuit.

[0008] In one embodiment, a disclosed method for generating current-limited warning tones includes determining whether a transceiver is in a transmit state, the transceiver configured to process an audio signal representing a warning tone, determining whether an audio volume level setting exceeds a threshold associated with an intensity of the warning tone, adjusting a peak-to-peak amplitude of the audio signal thereby representing the warning tone, generating a reduced audio signal based on the adjustment of the peak-to-peak amplitude of the audio signal, reducing the maximum amplitude of the reduced audio signal, and generating an adjusted audio signal based on the reduction of the maximum amplitude of the reduced audio signal.Adjusting the peak-to-peak amplitude and decreasing the maximum amplitude may be activated in response to determining that the transceiver is in the transmit state and determining that the audio volume level setting exceeds the threshold associated with the intensity of the tone.

[0009] In one embodiment, a disclosed audio generation unit for a portable communication device includes a warning tone current limiting controller and a current limiting trigger circuit coupled to the warning tone current limiting controller. The warning tone current limiting controller may include a voltage scaling controller and a warning tone amplitude modulator. The voltage scaling controller may be configured to generate a reduced audio signal by adjusting the peak-to-peak amplitude of an audio signal representing a warning tone. The warning tone amplitude modulator may be configured to generate an adjusted audio signal by reducing the maximum amplitude of the reduced audio signal.The current limit trigger circuit may be configured to activate the alert tone current limit controller in response to determining that a transceiver for processing the audio signal representing the alert tone is in a transmit state, and determining that an audio volume level setting exceeds a threshold associated with an intensity of the alert tone.

[0010] In at least some embodiments of the present disclosure, the systems, methods, and devices described herein for reducing a peak instantaneous current of a communication device may limit the reduction in the device's peak instantaneous current to periods during which the warning tones are reproduced. Unlike devices that utilize warning tone volume reduction, the methods and devices described herein reproduce the warning tone at approximately the same loudness as the warning tone loudness without any reduction in the device's peak instantaneous current.

[0011] In at least some embodiments of the present disclosure, the systems, methods, and devices described herein for reducing a communication device's peak instantaneous current may limit monitoring of the audio signal or the device's peak instantaneous current to periods during which the alert tones are reproduced. Unlike devices that require constant monitoring of the device's audio signal and current, the methods and devices described herein may wait until one or more conditions are met before monitoring the audio signal or the device's peak instantaneous current. The conditions may include, without limitation, whether a transmission event is about to occur and whether the alert audio volume level setting exceeds a threshold.

[0012] In at least some embodiments of the present invention, the systems, methods, and devices described herein for reducing peak instantaneous current of a communication device may operate without any intermediate energy storage. Unlike devices that use a capacitor or larger battery as an energy storage device to amplify audio output, creating hazardous conditions in Division 1 environments or other environmental standards, the methods and devices described herein may reduce peak instantaneous current of the communication device while satisfying intrinsic safety standards for operation in Division 1 environments (e.g., UL standards, ATEX standards).

[0013] In at least some embodiments of the present invention, the systems, methods, and devices described herein for reducing a communication device's peak instantaneous current can operate without requiring a delay of the audio signal. Unlike devices that implement audio delays to reduce the device's root mean square (RMS) current, the methods and devices described herein can reduce a communication device's peak instantaneous current within a microsecond without requiring any added delay, which could be dangerous in hazardous environments or during emergencies.

[0014] In at least some embodiments of the present disclosure, the systems, methods, and devices described herein for reducing a peak instantaneous current of a communication device may adjust the audio signal prior to amplification by an audio amplifier. Unlike devices that implement changes in audio gain, the systems, methods, and devices described herein may adjust the source audio signal to provide a resulting audio signal without any substantial reduction in gain of the resulting audio signal.

[0015] In at least some embodiments of the present disclosure, the systems, methods, and devices described herein for reducing peak instantaneous current of a communication device may process warning tones simultaneously with other audio events. Unlike devices that drive the device's power output to the widest possible range, the systems, methods, and devices described herein account for the high peak instantaneous current during simultaneous events, such as the output of an audio signal and the warning tone. Additionally, the systems, methods, and devices described herein may operate with any type of amplifier, including, but not limited to, linear and non-linear amplifiers.

[0016] It will now Fig. 1A, a front perspective view of an exemplary portable communication device 100 with peak instantaneous current reduction for warning tones is provided, constructed according to some embodiments. In various embodiments, portable communication device 100 may include an antenna 105 for transmitting and receiving one or more communication signals. Antenna 105 may communicate using one or more communication standards, including, but not limited to, radio communication and wireless communication. Portable communication device 100 may further include a battery 135. Battery 135 may be embedded within portable communication device 100 (not shown) or may be removable from portable communication device 100. Battery 135 may be charged via one or more ports 140.

[0017] In various embodiments, the portable communication device 100 may include one or more input devices. In some embodiments, a plurality of front-panel buttons 130 may be used to input information into the portable communication device 100. In various embodiments, one or more microphones 120 may be used to receive audio input into the portable communication device 100. In some embodiments, a primary display 125 of the portable communication device 100 may include a touch input interface to control the portable communication device 100. In some embodiments, the portable communication device 100 may include one or more buttons (110 and 115). For example, button 110 may be used to adjust the volume of the audio output of the portable communication device 100, such as the volume of an alert tone.In another example, the button 115 may be used to set the communication channel used by the portable communication device 100.

[0018] It will now Fig. 1B, a rear perspective view of an exemplary portable communication device 100 with peak instantaneous current reduction for warning tones is provided, constructed in accordance with some embodiments. The portable communication device 100 may include a secondary display 160 that may provide information about one or more communication signals, such as the communication channel of the portable communication device 100. The portable communication device 100 may include one or more microphones 165 to receive audio input and one or more speakers 145 to output sound. The speakers 145 may output sound for warning tones corresponding to two-way radio transmissions or one or more emergency communication signals. In some embodiments, the portable communication device 100 may include one or more side buttons (150 and 155) for communications.For example, side button 150 may provide PTT ("push-to-talk") functionality for portable communication device 100. Push-to-talk may be utilized with any suitable communication protocol to enable one or more two-way radio communication signals. Activation of side button 150 may result in the output of an alert tone and the transmission of one or more radio communication signals. In another example, side button 155 may be a programmable input assigned to a specific function by a user.

[0019] It will now Fig. 2, where a block diagram is provided illustrating an example of a portable communication device 200 with peak instantaneous current reduction for warning signals, according to some embodiments. Fig. 2, a battery 235 may provide power to the portable communication device 200 via a power supply 202. The battery 235 and the power supply 202 may be coupled by the positive battery terminal B+ 224 and the negative battery terminal B- 226. The battery 235 may also provide data to the power supply 202 or other parts of the portable communication device 200 via a data line D 228. The power supply 202 may include one or more components to convert the voltage provided by the battery 235 into a supply voltage V CC232 for use by other parts of the portable communication device 200. For example, the power supply 202 may include a power management integrated circuit (PMIC) that may provide information about the battery 235, such as the charge level of the battery 235, to a processor 204 via a data signal D 234. In another example, the power supply 202 may include a switched mode power supply (SMPS) that may provide a five-volt (5V) supply to other parts of the portable communication device 200. In various embodiments, an SMPS may be a component that may or may not be integrated with a PMIC or other components within the power supply 202.In another example, power supply 202 may include a power-up circuit that may monitor the terminal voltage (224 or 226) of battery 235 and generate a power-up signal for portable communication device 200 based on various types of information from battery 235, such as the voltage of positive terminal B+ 224 and information provided on data line D 228. In some embodiments, a power-up circuit may be implemented using a microcontroller to perform a more intelligent or context-aware assessment of the capacity of battery 235 than a comparator that determines whether the voltage of positive terminal B+ 224 is above a predefined reference voltage.

[0020] In various embodiments, the portable communication device 200 may include a processor 204 that uses energy from the supply voltage V CC232 operates. As illustrated in this exemplary embodiment, the processor 204 may be coupled to a variety of components, such as a memory 206, a power supply 202, a transceiver 208, an alert tone volume control 210, a PTT button 250, and a current limit trigger circuit 214. In various embodiments, the processor 204 may include a microprocessor, a microcontroller, a system on a chip, a field-programmable gate array, a programmable mixed-signal array, or, in general, any system or subsystem that includes nominal memory and is capable of executing a sequence of instructions to control hardware.In various embodiments, memory 206 may include read-only memory (ROM), random access memory (RAM), static random access memory (SRAM), and dynamic random access memory (DRAM). Transceiver 208 may be coupled to processor 204 via memory 206 (not shown) or directly coupled through an input / output interface 236 to process an audio signal that may represent a warning tone. Antenna 205 may be coupled to transceiver 208 to receive and transmit communication signals. In some embodiments, a warning tone may be generated by activation of a PTT button 250, which may indicate the activation to processor 204 via signal 264.The alert volume control 210 may control the volume of one or more types of audio information, such as alert tones and one or more audio communication signals output from the speaker 245 of the portable communication device 200. In some embodiments, the alert volume control 210 may be coupled to an analog-to-digital converter (ADC) to translate an analog value indicative of the physical position of the alert volume control 210 into a digital value that is transmitted to the processor 204 via the signal 212. In some embodiments, the alert volume control 210 may be implemented using instructions executing on the processor 204 to provide a virtual volume control for alert tones.

[0021] The alert tone volume control 210 can control the volume of alert tones generated for various purposes, including, but not limited to, an indication of receipt of a transmission, such as a private or selective call or message, an indication of an acknowledgment to or from a dispatcher, an indication of a PTT event, such as a transmit event or a reject event, an indication of an emergency event, an indication of warning events, such as a transmission timeout event or a low battery event, an indication of an evacuation event, beep transmissions, such as dual-tone multi-frequency tones, or an indication of an announcement event, such as situations where the radio moves out of radio coverage.Warning tones, such as talk permit tones (TPTs) and time-out timer tones (TOTs), may be emitted by the portable communication device 200 concurrently with other audio output, such as the audio transmissions received by the transceiver 208. When warning tones are emitted concurrently with other audio output, the peak instantaneous current consumed by the portable communication device 200 may exceed the maximum peak instantaneous current threshold, which may be defined by one or more standards. For example, the UL safety body requirement for Division 1 devices operating in hazardous environments may limit the maximum peak instantaneous current threshold over a defined period of time.As the functionality of portable communication devices 200 increases, components other than those responsible for audio output (e.g., transceiver 208 and speaker 245) may consume more peak instantaneous current. In various embodiments, the maximum peak instantaneous current threshold may be limited to values ​​less than the peak instantaneous current requirement for portable communication device 200. For example, if the maximum device threshold of peak instantaneous current is limited to 4 amps, the audio output may be limited to 1.8 amps or less. In various embodiments, current limit trigger circuit 214 may activate alert tone current limit controller 218 to limit the maximum peak instantaneous current threshold of the audio output without requiring the perceived loudness of the alert tones to be reduced.Current limit trigger circuit 214 may receive a variety of signals from processor 204. For example, processor 204 may provide a signal 242 based on a determination of whether transceiver 208 is in a transmit state, which may consume additional power, and a signal 242 indicating the result of the determination. In another example, processor 204 may provide a signal 244 based on a determination of whether the audio volume level corresponding to warning tones, which may be adjusted by warning tone volume control 210, exceeds a threshold associated with an intensity of warning tones.

[0022] In various embodiments, current limit trigger circuit 214 may receive one or more signals indicative of the current provided by battery 235 to other parts of portable communication device 200. For example, current limit trigger circuit 214 may receive a signal 246 from processor 204, which may receive information about data signal D 234 from power supply 202. Power supply 202 or processor 204 may provide an estimate of the current provided by battery 235 based on any signal indicative of the current, including, but not limited to, the duty cycle of a switch in power supply 202.In another example, the current limit trigger circuit 214 may receive a signal 252 from the power supply 202, which may measure the current provided by any suitable means, including, but not limited to, a series resistance, and provide the current limit trigger circuit 214 with a value indicative of the measured current. In another example, the current limit trigger circuit 214 may receive a signal 254 from the battery 235, which may measure a voltage drop associated with a current flowing through an impedance of the battery 235, and provide the current limit trigger circuit 214 with a value indicative of the voltage drop.

[0023] Current limit trigger circuit 214 may determine, in response to the plurality of received signals, whether to activate alert tone current limit controller 218. For example, current limit trigger circuit 214 may activate alert tone current limit controller 218 in response to signals 242 and 244 to reduce the current consumption associated with audio output. Signal 242 may indicate that processor 204 has determined that transceiver 208 is in a transmit state, and signal 244 may indicate that processor 204 has determined that the audio volume level corresponding to alert tones exceeds a threshold associated with an intensity of the alert tones.

[0024] If signal 242 does not indicate that transceiver 208 is in a transmit state, or signal 244 does not indicate that the audio volume level corresponding to warning tones exceeds the threshold, current limit trigger circuit 214 may disable adjustment by warning tone current limit controller 218 to pass the audio signal through so that it is output without reducing the power consumption associated with audio output of warning tones. In another example, current limit trigger circuit 214 may activate warning tone current limit controller 218 in response to signal 242, 244, and at least one of signals 246, 252, and 254. The current limit trigger circuit 214 may compare one or more signals (246, 252, and 254) indicative of the current supplied by the battery 235 to one or more thresholds associated with current consumption.For example, if the one or more signals indicate that the current supplied by battery 235 exceeds the maximum allowable peak instantaneous current during a period of time, as defined by one or more safety standards, current limit trigger circuit 214 may activate warning tone current limit controller 218 to reduce the current consumption associated with an audio output. In other embodiments, current limit trigger circuit 214 may provide a value indicative of the current supplied by battery 235 to warning tone current limit controller 218 via signal 248 to adjust the amount of reduction in current consumption associated with an audio output of warning tones.

[0025] When enabled by current limit trigger circuit 214 to reduce the power consumption associated with audio output, warning tone current limit controller 218 may modify the audio signal 256 provided by audio source 216 and provide an adjusted audio signal 258 to audio amplifier 222, which may generate an amplified audio signal 262 for speaker 245. Warning tone current limit controller 218 may pass audio signal 256 without adjustment when adjustment by current limit trigger circuit 214 is disabled. For example, warning tone current limit controller 218 may include a bypass controller 257 that may pass audio signal 256 from audio source 216 to audio amplifier 222 via an adjusted audio signal 258.The bypass controller 257 may be implemented using a multiplexer or any circuit, a digital signal processor (DSP), or a field-programmable gate array (FPGA) configured to pass the audio signal 256 when adjustment by the current-limit trigger circuit 214 is disabled. Those skilled in the art will appreciate that in some embodiments, the bypass controller 257 may be integrated with the alert tone current-limit controller 218.

[0026] In some embodiments, the warning tone current limit controller may receive a value indicative of the current supplied by battery 235 via a signal 248, and may vary the amount of adjustment of the audio signal in response to the amount of power consumed by portable communication device 200. For example, in cases where portable communication device 200 consumes more than the maximum peak instantaneous current permitted by one or more safety standards, warning tone current limit controller 218 may provide a greater amount of adjustment of the audio signal compared to cases where portable communication device 200 consumes less power.In various embodiments, the warning tone current limit controller 218 may include a plurality of circuits for adapting an analog audio signal, or a digital signal processor (SDP) or a field programmable gate array (FPGA) configured to adapt a digital audio signal. In various embodiments, the audio source 216 may generate a sinusoidal signal and may include a microprocessor, a DSP, a field programmable gate array (FPGA), or circuitry to generate an audio signal with a specified amplitude and frequency. In some embodiments, a digital audio source may be converted to an analog audio signal using a digital-to-analog converter (DAC).

[0027] It will now Fig. 3, a block diagram is provided illustrating an exemplary alert tone current limit controller 318 configured in accordance with some embodiments. The alert tone current limit controller 318 may be part of an audio generation unit 300. As illustrated in this exemplary embodiment, the alert tone current limit controller 318 may be activated via a signal 348 by a current limit trigger circuit 314, and may include a limiting factor selector 366, a voltage scaling controller 368, and an alert tone amplitude modulator 372. The current limit trigger circuit 314 may receive 342, 344, as well as one or more of the signals 346, 352, and 354. The alert tone current limit controller 318 may be activated by one or more comparisons in the current limit trigger circuit 314.For example, current limit trigger circuit 314 may compare one or more inputs to one or more thresholds 378 using one or more comparators 380, which may output one or more indications regarding current consumption via signal 348 to activate alert current limit controller 318. Although no comparator is shown, current limit trigger circuit 314 may utilize any circuit structure suitable for comparing one or more inputs to a threshold.

[0028] Limiting factor selector 366 may determine the alert tone adjustment level to be performed on audio signal 356 based on signal 348, which may indicate one or more triggers, including, but not limited to, whether the transceiver associated with audio generation unit 300 is in a transmit state, whether the audio volume level corresponding to alert tones exceeds one or more thresholds, and whether the amount of current supplied by a battery associated with audio generation unit 300 exceeds one or more thresholds. For example, signal 348 may indicate triggers for the transceiver being in a transmit state and the audio volume level corresponding to alert tones exceeding one or more thresholds.In another example, signal 348 may indicate triggers that the transceiver is in a transmit state and that the audio volume level corresponding to warning tones exceeds one or more associated thresholds, and the amount of peak instantaneous current provided exceeds one or more associated thresholds.

[0029] In some embodiments, the limiting factor selector 366 may include a predefined lookup table or a database. For example, Table 1 shows a variety of warning tone adjustment levels corresponding to different values ​​of peak instantaneous current. Table 1. Warntonanpassungsniveau Spitzenmomentanstrom(Ampere) Warntonlautheit(dB SPL) 0 1,8 93 1 1,2 91 2 0,8 90 3 0,6 85

[0030] Although four adjustment levels are shown, the limiting factor selector may include any suitable number of adjustment levels. As shown in Table 1, alert tone adjustment level 0, which represents no adjustment of the audio signal 356, corresponds to the amount of peak instantaneous current of 1.8 amperes consumed for audio output from the portable communication device. Alert tone adjustment level 0 may result in a maximum alert tone loudness of 93 decibels (dB) of the sound pressure level (SPL). The limiting factor selector 366 of the alert tone current limiting controller 318 may reduce the amount of peak instantaneous current by selecting a different alert tone adjustment level.For example, the amount of peak instantaneous current provided by the portable communication device may exceed 4 amperes, resulting in selection of alert tone adjustment level 3, which reduces the peak instantaneous current consumed for audio outputs from the portable communication device to 0.6 amperes while maintaining the same perceived loudness at a maximum alert tone loudness of 85 dB SPL.

[0031] In various embodiments, the voltage scaling controller 368 may receive a signal 374 from the limiting factor selector 366 and an audio signal 356 from the audio source 316. The signal 374 may include one or more indications regarding the alert tone adjustment level. For example, the signal 374 may indicate the alert tone adjustment level. In another example, the signal 374 may indicate the maximum threshold of the peak instantaneous current or the alert tone loudness. In another example, the signal 374 may indicate the associated adjustment to be applied to the voltage scaling controller 368. In various embodiments, the voltage scaling controller 368 may adjust a peak-to-peak amplitude of the alert tone associated with the audio signal 348.For example, if the alert tone adjustment level corresponding to a maximum peak instantaneous current threshold of 1.8 amperes is received, the voltage scaling controller 368 may maintain a unity gain of the peak-to-peak amplitude of the alert tone associated with the audio signal 348. In another example, if an alert tone adjustment level corresponding to a maximum peak instantaneous current threshold of 0.6 amperes is received, the voltage scaling controller 368 may decrease the gain of the peak-to-peak amplitude of the alert tone associated with the audio signal 348.In various embodiments, voltage scaling controller 368 may be an analog circuit for adjusting the peak-to-peak amplitude of an analog audio signal, or a digital signal processor (DSP) or a field-programmable gate array (FPGA) configured to adjust the peak-to-peak amplitude of a digital audio signal. For example, voltage scaling controller 368 may include a unity gain buffer 382 and a voltage divider 384 to reduce the peak-to-peak amplitude of the warning tone. Voltage divider 384 may be adjusted based on signal 374 to adjust the gain of the output to extend the peak-to-peak amplitude of the warning tone.Although buffer 382 and divider 384 are not shown, voltage scaling controller 368 may be implemented using any circuit, DSP, or FPGA suitable for adjusting the peak-to-peak amplitude of an audio signal based on signal 374.

[0032] In various embodiments, the voltage scaling controller 368 may provide a signal 376 to the alert tone amplitude modulator 372. The signal 376 may include an audio signal modified by the voltage scaling controller 368, as well as one or more indications of the alert tone adjustment level, such as the one or more indications described for the signal 374. In various embodiments, the alert tone amplitude modulator 372 may be implemented in a circuit to process an analog signal or a digital signal. For example, the alert tone amplitude modulator 372 may be implemented using diodes 386 and 388, which collectively form a diode clipping circuit to process an analog signal.The diode clipping circuit may clip an audio signal through diode 386, clipping the positive portions of the audio signal, and through diode 388, clipping the negative portions of the audio signal. Although a diode clipping circuit is shown, the warning tone amplitude modulator 372 may be implemented using any circuit, DSP, or FPGA suitable for adjusting the amplitude of the warning tone. For example, a DSP may tightly limit the audio signal associated with the warning tone when the audio signal exceeds a threshold.

[0033] The alert tone amplitude modulator 372 may limit the peaks of the audio signal modified by the voltage scaling controller 368 by clipping or hard limiting the amplitude of the alert tone. For example, the alert tone amplitude modulator 372 may convert the sinusoidal signal associated with the audio signal modified by the voltage scaling controller 368 into a hard-limited signal with a limited amplitude of the alert tone. In various embodiments, the alert tone amplitude modulator 372 may limit the amplitude of the alert tone based on the one or more cues provided with the signal 376.For example, if an alert corresponds to a maximum peak instantaneous current threshold of 1.8 amperes, the alert tone amplitude modulator 372 may maintain the amplitude of the alert tone without hard limiting or clipping the peaks of the sine wave. In another example, if an alert corresponds to a maximum peak instantaneous current threshold of 0.6 amperes, the alert tone amplitude modulator 372 may limit the amplitude of the alert tone, which may clip or hard limit the peaks of the sine wave to produce a signal that is substantially a square wave. Based on the one or more alerts provided by the signal 376, the alert tone amplitude modulator 372 may generate an adjusted audio signal 358 that is received by the audio amplifier 322.The adjusted audio signal 358 may be amplified by the audio amplifier 322 to generate an amplified audio signal 362 for the speaker 345. In various embodiments, the audio amplifier 322 may achieve amplification of the adjusted audio signal 358 using any suitable circuitry, including, but not limited to, Class D amplification.

[0034] It will now Fig. 4, a flowchart of an exemplary method 400 for reducing a peak instantaneous current for warning tones is provided, which is illustrated in accordance with some embodiments. While in Fig. 4, a specific order of operations is provided for illustrative purposes, the timing or ordering of such operations may vary as appropriate without negating the purpose and advantages of the examples detailed in the remainder of this disclosure. In some embodiments, one or more portions of method 400 may be executed at any predetermined periodic subsequent time period in response to a trigger occurring locally within the portable communication device. For example, the trigger may occur in response to a need to generate an alert tone.

[0035] In this exemplary embodiment, the method 400 begins with block 401 in Fig. 4, and it continues with block 405, where it is determined whether a transceiver of the portable communication device, such as the one in Fig. 2, is in a transmit state. The determination of block 405 may be performed by one or more components of the portable communication device. For example, a current limit trigger circuit, such as current limit trigger circuit 214 as shown in Fig. 2, or the current limit trigger circuit 314 as described in Fig. 3, receive information about the state of the transceiver, such as by the processor 204 as described in Fig. 2. In another example, one or more instructions executed by a processor of the portable communication device, such as processor 204 as described in Fig. 2, determine the status of the transceiver.

[0036] In this example, in block 410, it may be determined whether an audio volume level setting exceeds a threshold associated with an intensity of a warning tone. The determination of block 410 may be performed by one or more components of the portable communication device. For example, a current limit trigger circuit, such as current limit trigger circuit 214 as shown in Fig. 2, or the current limit trigger circuit 314 as described in Fig. 3, receive information about the audio volume level setting. The current limit trigger circuit may include a comparator to compare the received information to a threshold associated with an intensity of a warning tone. The comparator may generate an output having a first value, such as a logic high, when the received information exceeds the threshold, and may generate an output having a second value, such as a logic low, when the received information does not exceed the threshold. In another example, one or more instructions executed by a processor of the portable communication device, such as processor 204 as described in Fig. 2, determine whether the audio volume level setting exceeds the threshold. The audio volume level setting can be adjusted using a volume control knob, such as knob 110, used in conjunction with the Fig. 1A and Fig. 1B, or by using the warning tone volume control 210 described in Fig. 2 is described.

[0037] At block 415, the determinations from blocks 405 and 410 may be evaluated. If the transceiver is in the transmit state and the audio volume level exceeds the threshold, the method 400 may proceed to block 420. Otherwise, the method 400 may return to block 405. At block 420, the peak-to-peak amplitude of an audio signal representing the warning tone may be adjusted. The adjustment may be performed by a voltage scaling controller of a warning tone current limiting controller, for example, by the voltage scaling controller 368 associated with Fig. 3. The adjustment may maintain the peak-to-peak amplitude with a unity gain, or it may decrease the peak-to-peak amplitude with a gain less than 1. At block 425, a decreased audio signal may be generated after the peak-to-peak amplitude is adjusted. The decreased audio signal may be generated by a voltage scaling controller, such as voltage scaling controller 368, which may be used in conjunction with Fig. 3. At block 430, the maximum amplitude of the reduced audio signal may be limited. The limitation may be performed by a warning tone amplitude modulator, such as the warning tone amplitude modulator 372 used in conjunction with Fig. 3. The restriction may clip or impose a hard limit on any portion of the audio signal above the maximum amplitude, and may maintain portions of the audio signal below the maximum amplitude. In some embodiments, the restriction may result in a conversion of a sine wave associated with the reduced audio signal to a signal that is substantially a square wave. At block 435, an adjusted audio signal may be generated after the maximum amplitude has been limited in block 430. The adjusted audio signal may be generated by an alert tone amplitude modulator, such as the alert tone amplitude modulator 372 described in connection with Fig. 3 is described.

[0038] It will now Fig. 5, a flowchart of an exemplary method 500 for variably reducing a peak instantaneous current for warning tones is provided, which is illustrated in accordance with some embodiments. While in Fig. 5, a specific order of operations is provided for illustrative purposes, the timing or ordering of such operations may vary as appropriate without negating the purpose and advantages of the examples detailed in the remainder of this disclosure. In some embodiments, one or more portions of method 500 may be executed at any predetermined periodic subsequent time period in response to a trigger occurring locally within the portable communication device. For example, the trigger may occur in response to a need to generate an alert tone.

[0039] In this exemplary embodiment, the method 500 begins with block 501 in Fig. 5, and continue with block 502 where an activation event is received corresponding to a generation of a warning tone. The activation event may be generated by one or more components of the portable communication device, such as the processor of the portable communication device. For example, movement of a button on the portable communication device may generate the activation event. The button may be a key or switch on the portable communication device, such as one of the plurality of front buttons 130 provided in connection with Fig. 1A, or one of the side buttons (150 or 155) used in connection with Fig. 1B, or by the processor of the portable communication device. In another example, the activation event may be generated by a processor of the portable communication device, such as processor 204 described in connection with Fig. 2, which may receive an event, including, but not limited to, receipt of a transmission, such as a private or selective call or message, receipt or transmission of an acknowledgment to or from a dispatcher, a virtual PTT event, or an indication of an emergency event. In some embodiments, activation may configure the transceiver to initiate a transmission. The method 500 may proceed to block 505 in response to receiving an activation event at block 502.

[0040] At block 505, it may be determined whether a transceiver of the portable communication device is in a transmit state, as described in connection with block 405 of Fig. 4. At block 510, it may be determined whether an audio volume level setting exceeds a threshold associated with an intensity of the warning tone, as described in connection with block 410 of Fig. 4. In block 515, the determinations from blocks 505 and 510 can be evaluated, as described in connection with block 415 of Fig. 4. The method 500 may proceed to block 516 if the transceiver is in the transmit state and the audio volume level exceeds the threshold. Otherwise, the method 500 may proceed to block 518 if the transceiver is not in the transmit state or if the audio volume level does not exceed the threshold.

[0041] At block 516, a value indicative of a current associated with the warning tone may be received. The current may be provided by a battery of the portable communication device, such as battery 135 associated with the Fig. 1A and Fig. 1B, or the battery 235, which is used in connection with Fig. 2. The value can be made available to a limiting factor selector, such as the limiting factor selector 366 used in conjunction with Fig. 3, which can receive the value from the current limit trigger circuit 314 via the signal 348, as in Fig. 3. If the portable communications device is designed to operate in Division 1 hazardous environments, the maximum current provided by the battery may be limited by safety standards, such as those promulgated by the UL safety body. These safety standards may further limit an intermediate energy storage device between the battery and a component of the portable communications device that requires additional peak instantaneous current. As described herein, the portable communications device may reduce a peak instantaneous current associated with warning tones and maintain the perceived loudness of the warning tone to satisfy safety standards and maintain communication in emergency situations.

[0042] At block 517, a warning tone adjustment level may be determined from a plurality of predetermined adjustment levels. The determination may be based on the received value indicative of the current associated with the warning tone. For example, if the value indicates that the portable communication device is consuming more power than the peak instantaneous current requirement, the maximum warning tone adjustment level may be used to reduce the current of warning tones. The warning tone adjustment level may be provided as a signal, such as signal 374, as in connection with Fig. 3, are provided for other components of the warning tone current limit controller.

[0043] If, at block 518, the transceiver is not in the transmit state or the audio volume level does not exceed the threshold, peak-to-peak amplitude adjustment and maximum amplitude limiting may be disabled. In some embodiments, the disabling may be controlled by a current limit trigger circuit, such as current limit trigger circuit 214, as described in connection with Fig. 2, or the current limiting trigger circuit 314, as described in connection with Fig. 3, which may control the activation of a peak instantaneous current reduction for warning tones within a few milliseconds of receiving the activation event, or the deactivation of an adjustment in response to the termination of the warning tone output. At block 519, a base warning tone adjustment level may be set to deactivate the adjustment of the audio signal representing the warning tone. For example, the base warning tone adjustment level may be the warning tone adjustment level 0, as described in connection with Table 1 and Fig. 3 is described.

[0044] At block 520, the peak-to-peak amplitude of an audio signal representing the warning tone may be adjusted based on the warning tone adjustment level determined by block 516 or set by block 519. As described in connection with block 420 of Fig. 4, a voltage scaling controller can perform the adjustment. The extent of adjustment can be based on the warning tone adjustment level. For example, with increasing warning tone adjustment level, as described in conjunction with Table 1 and Fig. 3, a greater degree of adjustment is applied to the peak-to-peak amplitude of the audio signal representing the warning tone. At block 525, a reduced audio signal is generated, as described in connection with block 425 of Fig. 4 is described.

[0045] At block 530, the maximum amplitude of the reduced audio signal may be limited based on the warning tone adjustment level determined by block 516 or set by block 519. As described in connection with block 430 of Fig. 4, a warning tone amplitude modulator may limit the maximum amplitude of the reduced audio signal. The level of the maximum amplitude may be based on the warning tone adjustment level. For example, with increasing warning tone adjustment level, as described in connection with Table 1 and Fig. 3, a lower maximum amplitude may be used to limit the reduced audio signal by a greater amount. At a warning tone adjustment level 3, as shown in Table 1, the peak instantaneous current may not be greater than 0.6 amperes. In this scenario, the sinusoidal shape of the reduced audio signal may be converted into a signal that is essentially a square wave by clipping or hard limiting the peaks of the sinusoidal shape. At block 535, an adjusted audio signal is generated, as described in connection with block 435 of Fig. 4 is described.

[0046] At block 540, the adjusted audio signal is amplified by an audio amplifier, such as audio amplifier 322, which is used in conjunction with Fig. 3 to generate an amplified audio signal. In various embodiments, the adjusted audio signal may be amplified independently of the warning tone adjustment level. At block 545, sound representing the warning tone may be output based on the amplified audio signal. In various embodiments, the sound may be output from a speaker, such as speaker 145 described in connection with Fig. 1B, the loudspeaker 245, which is used in connection with Fig. 2, or the loudspeaker 345, which is used in connection with Fig. 3 is described.

[0047] Specific embodiments have been described in the foregoing specification. However, it will be apparent to those skilled in the art that various modifications and changes may be made without departing from the spirit of the invention as set forth in the claims below. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present teachings.

[0048] The benefits, advantages, solutions to problems, and any conceivable element that results in any benefit, advantage, or solution occurring or becoming more pronounced are not to be construed as critical, required, or essential features or elements of any or all of the claims. The invention is defined solely by the appended claims, including any amendments made during the pendency of the present application, and all equivalents of such claims as published.

[0049] Furthermore, in this document, relational expressions such as first and second, top and bottom, and the like are intended to be used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "comprises," "comprising," "has," "having," "include," "containing," "contain," "containing," or any variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising, having, including, or containing a list of elements may include not only such elements, but may include other elements not expressly listed or inherent in such processes, methods, articles, or devices. An element that continues with "comprises... a," "has...a", "includes... a", "contains... a", does not, without further qualification, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprise, have, include, or contain the element. The terms "a" and "an" are defined as one or more unless explicitly stated otherwise herein. The terms "substantially", "essentially", "approximately", "about", or any other version thereof have been defined as "being close to" as would be understood by one of ordinary skill in the art, and in one non-limiting embodiment, the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1%, and in another embodiment within 0.5%. The term "coupled," as used herein, is defined as "connected," although not necessarily directly and not necessarily mechanically.A device or structure that is "configured" in a particular way is configured in at least that way, but may also be configured in at least one way that is not listed.

[0050] It is desired that some embodiments include one or more generic or specialized processors (or "processing devices"), such as microprocessors, digital signal processors, custom processors, and field-programmable gate arrays (FPGAs), and unique stored program instructions (including both software and firmware) that control the one or more processors to, in conjunction with certain non-processor circuitry, implement some, most, or all of the functions of the method and / or apparatus described herein.Alternatively, some or all of the functions may be implemented by a state machine that has no stored program instructions, or in one or more application-specific integrated circuits (ASICs) in which each function, or some combination of certain of the functions, is implemented as custom logic. Of course, a combination of the two approaches can be used. Both the state machine and the ASIC are considered "processing devices" herein, both for the purposes of the above discussion and the claims.

[0051] Furthermore, an embodiment may be implemented as a computer-readable storage medium having computer-readable code stored thereon for programming a computer (e.g., including a processor) to perform a method described and claimed herein. Examples of such computer-readable storage media include, but are not limited to, a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a ROM (Read Only Memory), a PROM (Programmable Read Only Memory), an EPROM (Erasable Programmable Read Only Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory), and a flash memory.Furthermore, it is expected that one skilled in the art, notwithstanding possible considerable effort and a wide range of design choices due, for example, to available time, current technology, and economic considerations, guided by the concepts and principles disclosed herein, will readily be able to create such software instructions and programs and ICs with minimal experimentation.

[0052] The Summary of Disclosure is provided to allow the reader to quickly appreciate the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the spirit or meaning of the claims. Additionally, it will be appreciated from the foregoing Detailed Description that various features in various embodiments are grouped together to streamline the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as will be apparent from the following claims, inventive subject matter is found in fewer than all features of a single disclosed embodiment.Thus, the following claims are hereby incorporated into the detailed description, with each claim standing on its own as separately claimed subject matter.

Claims

[1] Portable two-way radio (100), comprising: a transceiver (208) configured to process an audio signal representing a warning tone; a processor (204) coupled to the transceiver (208), the processor (204) configured to: Determining (405) whether the transceiver (208) is in a transmit state; and Determining (410) whether an audio volume level setting exceeds a threshold associated with an intensity of the alert tone; a current limit trigger circuit (214, 314) coupled to the processor (204); and a warning tone current limit controller (218, 318), wherein the current limit trigger circuit (214, 314) is configured to activate the warning tone current limit controller (218, 318) in response to determining (405) that the transceiver (208) is in the transmit state and determining (410) that the audio volume level setting exceeds the threshold associated with the intensity of the warning tone, the warning tone current limit controller (218, 318) comprising: a voltage scaling controller (368) configured to generate a reduced audio signal by adjusting a peak-to-peak amplitude of the audio signal representing the warning tone in response to activation by the current limiting trigger circuit (214, 314); and a warning tone amplitude modulator (372) configured to generate an adjusted audio signal by limiting the maximum amplitude of the reduced audio signal in response to activation by the current limiting trigger circuit (214, 314). [2] A portable two-way radio (100) according to claim 1, further comprising: a battery (135) configured to provide power to the portable two-way radio (100), wherein the warning tone current limit controller (218, 318) further comprises a limiting factor selector (366) configured to: Receiving (516) a value indicative of the current provided by the battery (135); and Determining (517) a warning tone adjustment level from a plurality of predetermined adjustment levels, the determination being based on the value indicative of the current provided by the battery (135), wherein the warning tone amplitude modulator (372) is configured to limit the maximum amplitude of the reduced audio signal based on the warning tone adjustment level. [3] A portable two-way radio (100) according to claim 1, further comprising: an audio amplifier circuit coupled to the warning tone current limiting controller (218, 318), the audio amplifier (322) being configured to amplify the adjusted audio signal generated by the warning tone amplitude modulator (372) of the warning tone current limiting controller (218, 318); and a speaker (145, 245) configured to output sound representing the warning tone, the sound being based on the adjusted audio signal amplified by the audio amplifier (322). [4] The portable two-way radio (100) of claim 1, wherein the warning tone current limit controller (218, 318) is configured by the current limit trigger circuit (214, 314) to pass the audio signal representing the warning tone in response to at least one of the following: determining (505) that the transceiver (208) is not in the transmit state; and determining (510) that the audio volume level setting does not exceed the threshold associated with the intensity of the alert tone. [5] The portable two-way radio (100) of claim 1, wherein the alert tone amplitude modulator (372) is configured to limit the maximum amplitude of the reduced audio signal by hard limiting the reduced audio signal. [6] A portable two-way radio (100) according to claim 1, further comprising: a button (250), wherein the audio signal representing the warning tone is to be processed in response to activation of the button (250). [7] The portable two-way radio (100) of claim 1, wherein the audio signal representing the sound is a digital signal. [8] A method (400, 500) for generating current-limited warning tones, comprising: Determining (405, 505) whether a transceiver (208) is in a transmit state, the transceiver (208) being configured to process an audio signal representing a warning tone; Determining (410, 510) whether an audio volume level setting exceeds a threshold associated with an intensity of the alert tone; Adjusting (420, 520) a peak-to-peak amplitude of the audio signal representing the warning tone, wherein the adjustment (420, 520) is activated in response to determining (415, 515) that the transceiver is in the transmit state and determining that the audio volume level setting exceeds the threshold associated with an intensity of the tone; Generating (425, 525) a reduced audio signal based on adjusting (420, 525) the peak-to-peak amplitude of the audio signal; and Limiting (430, 530) the maximum amplitude of the reduced audio signal, wherein the limiting (430, 530) is activated in response to determining (415, 515) that the transceiver is in the transmit state and determining that the audio volume level setting exceeds the threshold associated with the intensity of the sound; Generating (435, 535) an adjusted audio signal based on limiting the maximum amplitude of the reduced audio signal. [9] The method of claim 8, further comprising: Receiving (516) a value indicative of power associated with the warning tone, the power being provided by a battery (135); and Determining (517) a warning tone adjustment level from a plurality of predetermined adjustment levels, wherein the determining is based on the value indicative of the current provided by the battery (135), wherein limiting the maximum amplitude of the reduced audio signal is based on the warning tone adjustment level. [10] The method of claim 8, further comprising: amplifying (540) the adjusted audio signal to produce an amplified audio signal; and Outputting (545) sound representing the warning tone, the sound being based on the amplified audio signal. [11] The method of claim 8, further comprising: Disabling the adjustment of the peak-to-peak amplitude of the audio signal and the limiting of the maximum amplitude of the reduced audio signal in response to at least one of the following: determining (405, 505) that the transceiver (208) is not in the transmit state; and determining (410, 510) that the audio volume level setting does not exceed the threshold associated with the intensity of the warning tone. [12] The method of claim 8, wherein the maximum amplitude of the reduced audio signal is limited by hard limiting the audio signal. [13] The method of claim 8, further comprising: Receiving (502) an activation event corresponding to generation of the warning tone, wherein determining (505) that the transceiver (208) is in a transmit state is performed in response to receiving (502) the activation event. [14] The method of claim 8, wherein the audio signal representing the warning tone is a digital signal. [15] Portable two-way radio (100), comprising: a transceiver (208) configured to process an audio signal representing a warning tone; a processor (204) coupled to the transceiver (208), the processor (204) configured to determine whether an audio volume level setting exceeds a predetermined threshold; and a warning tone current limit controller (218, 318) coupled to the processor (204), wherein the warning tone current limit controller (218, 318) is activated based on a determination by the processor (204) that the audio volume level setting exceeds the predetermined threshold, wherein the warning tone current limit controller (218, 318) is configured to: Reducing an audio signal by adjusting (520) the peak-to-peak amplitude of the audio signal, wherein the adjusting is based on the activation of the warning tone controller; and Generating (535) an adjusted audio signal by limiting the maximum amplitude of the reduced audio signal, wherein the limiting is based on the activation of the warning tone controller. [16] A portable two-way radio (100) according to claim 15, further comprising: a battery (135) configured to provide power to the portable two-way radio (135), wherein the warning tone current limit controller (218, 318) further comprises a limiting factor selector (366) configured to: Receiving (516) a value indicative of the current provided by the battery (135); and Determining (517) a warning tone adjustment level from a plurality of predetermined adjustment levels, wherein the determining (517) is based on the value indicative of the current provided by the battery (135), wherein limiting the maximum amplitude of the reduced audio signal is based on the warning tone adjustment level. [17] A portable two-way radio (100) according to claim 15, further comprising: an audio amplifier circuit coupled to the warning tone current limit controller (218, 318), the audio amplifier (322) configured to amplify the adjusted audio signal; and a speaker (245) configured to output sound representing the warning tone, the sound being based on the audio signal amplified by the audio amplifier (322). [18] The portable two-way radio (100) of claim 15, wherein the warning tone current limit controller (218, 318) is configured to pass the audio signal representing the warning tone based on at least one of the following: determining (505), by the processor (204), that the transceiver (208) is not in the transmit state; and determining (510) that the audio volume level setting does not exceed the predetermined threshold. [19] The portable two-way radio (100) of claim 15, wherein the alert tone controller (372) is configured to limit the maximum amplitude of the reduced audio signal by hard limiting the reduced audio signal. [20] A portable two-way radio (100) according to claim 15, further comprising: a button (250), wherein the audio signal representing the warning tone is to be processed in response to activation of the button (250). [21] The portable two-way radio (100) of claim 15, wherein the audio signal representing the sound is a digital signal. [22] A method (400, 500) for generating a current-limited warning tone of a portable radio device (100), comprising: Reducing an audio signal representing a warning tone by adjusting (420, 520) a peak-to-peak amplitude of the audio signal based on an audio volume level setting of a portable radio device (100) exceeding a predetermined threshold; and Generating (435, 535) an adjusted audio signal by limiting (430, 530) the maximum amplitude of the reduced audio signal based on the audio volume level setting exceeding the predetermined threshold. [23] The method of claim 22, further comprising: Receiving (516) a value indicative of a current associated with the warning tone, the current being provided by a battery (135); and Determining (517) a warning tone adjustment level from a plurality of predetermined adjustment levels, wherein the determining (517) is based on the current provided by the battery (135), wherein limiting the maximum amplitude of the reduced audio signal is based on the warning tone adjustment level. [24] The method of claim 22, further comprising: amplifying (540) the adjusted audio signal to generate an amplified audio signal; and Outputting (545) sound representing the warning tone, the sound being based on the amplified audio signal. [25] The method of claim 22, further comprising: Deactivating (518) the adjustment of the peak-to-peak amplitude of the audio signal and the limiting of the maximum amplitude of the reduced audio signal in response to at least one of the following: determining (505) that the transceiver (208) is not in the transmit state; and determining (510) that the audio volume level setting does not exceed the threshold associated with the intensity of the alert tone. [26] The method of claim 22, wherein the maximum amplitude of the reduced audio signal is limited by hard limiting the reduced audio signal. [27] The method of claim 22, further comprising: Receiving (502) an activation event corresponding to generation of the warning tone, wherein determining (505) that the transceiver (208) is in a transmit state is performed in response to receiving the activation event. [28] The method of claim 22, wherein the audio signal representing the warning tone is a digital signal. [29] Audio generating unit (300) for a portable communication device (100), comprising: a warning tone current limit controller (218, 318) configured to: Reducing an audio signal representing a warning tone by adjusting (520) a peak-to-peak amplitude of the audio signal; and generating (535) an adjusted audio signal by limiting the maximum amplitude of the reduced audio signal; and a current limit trigger circuit (214, 314) coupled to the warning tone current limit controller (218, 318), the current limit circuit being configured to activate the warning tone current limit controller (218, 318) based on: determining (405, 505) that a transceiver (208) is in a transmit state, the transceiver (208) being arranged to process the audio signal representing the warning tone; and determining (410, 510) that an audio volume level setting exceeds a predetermined threshold. [30] The audio generation unit (300) of claim 29, wherein the warning tone current limiting controller (218, 318) further comprises a limiting factor selector (366) configured to: Receiving (516) a value indicative of a current provided by a battery (135) of the audio generating unit; and Determining (517) a warning tone adjustment level from a plurality of predetermined adjustment levels, wherein the determining (517) is based on the value indicative of the current provided to the audio generation unit (300), wherein limiting the maximum amplitude of the reduced audio signal is based on the warning tone adjustment level. [31] The audio generation unit (300) of claim 30, wherein the adjustment (420, 520) of the peak-to-peak amplitude of the audio signal is based on the warning tone adjustment level. [32] The audio generation unit (300) of claim 29, wherein the warning tone current limiting controller (218, 318) is further configured to pass the audio signal representing the warning tone based on at least one of the following: determining (405, 505) that the transceiver (208) is not in the transmit state; and determining (410, 510) that the audio volume level setting does not exceed the predetermined threshold. [33] The audio generation unit (300) of claim 29, wherein the warning tone current limiting controller (218, 318) is configured to limit the maximum amplitude of the reduced audio signal by hard limiting the reduced audio signal. [34] The audio generating unit (300) of claim 29, wherein the audio signal representing the warning tone is a digital signal.

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