Modem Control Apparatus for Accurate T0 Timer and CNG Timing
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Solution Overview
Problem
AT modems face challenges in executing flexible control required for real-time facsimile communications, particularly in accurately measuring the T0 timer and controlling the calling tone (CNG) output timing, which are crucial for approval and error handling in FAX communications.
Innovation Solution
A modem control apparatus and method that sets the modem in a voice mode before dialing, allowing accurate detection of dialing completion and subsequent switching to facsimile mode for controlled CNG output, using AT commands to manage the T0 timer and CNG timing independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the modem operates in FAX mode and issues an ATD command, then the modem automatically outputs a calling tone (CNG) after dialing completion, but the CCU cannot control the CNG output timing and accurately detect dialing end timing
Solution Approach 1:
The patent segments the dialing process into two distinct phases: a setup phase in voice mode where the ATD command is issued and dialing occurs, and a control phase in FAX mode where CNG output is triggered. This segmentation allows the CCU to separately manage dialing execution and CNG control, resolving the contradiction between automatic dialing convenience and timing detection accuracy.
Solution Approach 2:
The patent performs preliminary action by setting the modem to voice mode before issuing the ATD command, and preparing the FAX mode with CNG output parameters in advance. This preliminary configuration allows the system to accurately track dialing timing in voice mode and then seamlessly transition to controlled CNG output in FAX mode, improving both timing detection and control precision.
2Ease of operation
If the modem operates in FAX mode, then the CNG output timing is automatic and uncontrollable, but accurate control of CNG timing is required for effective communication trouble handling
Solution Approach 1:
The patent applies dynamics by making the modem mode configurable and switchable between voice and FAX modes. This dynamic switching capability allows the system to adapt CNG output behavior to different operational requirements: automatic CNG in FAX mode for normal operations, and controlled CNG timing in voice mode for trouble handling scenarios, thereby achieving both ease of operation and control flexibility.
Solution Approach 2:
The patent changes the operational parameter (modem mode) between voice and FAX modes to achieve different CNG output behaviors. By switching modes, the system can control whether CNG output is automatic or controllable, providing adaptability for different communication scenarios while maintaining ease of operation in each mode.
3Ease of operation
If the T0 timer measurement starts from the ATD command issuance timing, then the measurement is simple, but the measurement is inaccurate because the dial number output time varies with line type and digit count
Solution Approach 1:
The patent introduces an intermediary mechanism by using the modem's internal dialing completion notification as a mediator between the ATD command issuance and the T0 timer start. Instead of directly timing from command issuance, the system waits for the modem's confirmation that dialing is complete, then starts the T0 timer. This intermediary step ensures accurate timing regardless of dial number length or line type, while maintaining operational simplicity through automated modem feedback.
Data Source
AI summary
This invention provides a mechanism which can attain at least one of an accurate measurement of a T0 timer and appropriate control of a CNG output timing in a FAX communication using AT commands. To accomplish this, in a modem control apparatus for controlling a modem using AT commands, the modem is set in a voice mode, an AT command including a dial number is sent to the modem set in the voice mode, the modem is set in a facsimile mode after completion of the dialing in the modem, and an AT command including no dial number is sent to the modem set in the facsimile mode so as to control the modem to begin to output a calling tone.