Telephone answering machine

Description

Call circle 14 is therefore blocked, and the JO device cannot be put into operation. When recording device 22 is connected correctly, it presents only a slight resistance to resistors A3 and Rf. and so that the current now flows via the resistor ^2 and the line 18a to the recording device 22. The associated voltage drop At the base of transistor T, this causes it to block. The ringing signals from the exchange line therefore reach the receiver via line 30. Call center 14, which automatically activates the telephone answering machine in a manner known per se. The caller is greeted by a recorded message. The tape recording initially stated that the telephone was not in use, but that a message would be recorded. can. Furthermore, the caller will be asked to state their message, which may be time-limited, after which counter 28 will be opened. The dashed position has been switched and contact M has closed. Full operating voltage is now applied to recording device 22. and the caller's message is recorded here. After the audio recording is finished, switches 28 and M are returned to their original position (usually by a timer switch) and the The operating sequence of the answering and recording device has ended. It is obvious that the transistor T, depending on the different resistance states at terminals 18a, 20, the recording device, which results there whether the recording device is connected or not connected in accordance with regulations, such as is controlled so that it maintains the connection between the telephone exchange line (a / b) and line 30 leading to call circle 14 or This prevents the switching device formed by the transistor is located in the answering machine. Since this switching device is located in the answering machine, the current and tone transmission cannot be interrupted. The necessary connection between devices 10 and 22 is established using a single cable 24. In this way, the components consisting of a The potential sources of error during commissioning of the devices, resulting from insufficient coupling, are significantly reduced. Finally, it should be mentioned that when using a counter that counts the calls arriving at the answering machine and After reaching a certain maximum number of these, the power supply to the sound recording device is cut off before the end of its tape storage capacity. interrupts, and another contact in line 18a is opened by the counter, whereby the transistor is switched on in the manner already described. T is put into a conductive state, call circuit 14 is blocked, and the entire device is thereby brought to a standstill. This includes 1 sheet of drawings.

Claims

Patent claims:

1. Telephone answering machine with a connectable audio recording device that draws its operating voltage from the answering machine receives, and with a device that monitors the connection or non-connection of the sound recording device, characterized in that the The call circuit (14) of the answering machine (10) includes an electronic switch forming the device (^) which is assigned depending on the different resistance states resulting at the connected or disconnected sound recording device (22) Connection points (18a. 20) for the audio recording device maintains the connection between the telephone exchange line (a, b) and the call circuit (14). or prevents it.

2. Telephone answering machine according to claim 1, characterized in that the electronic switch is provided by at least one transistor (T) is formed which, if the audio recording device (22) is not connected, blocks the call circle (14).

3. Telephone answering machine according to claim 1 or 2, characterized in that a single connecting cable (24) the The answering device (10) connects to the sound recording device (22), through which the power and sound supply is provided. The invention relates to a telephone answering machine with a connectable audio recording device, which derives its operating voltage received from the answering device, and with a device that monitors the connection or non-connection of the sound recording device. In a known device of this type, a call signal coming from the telephone line is used in a special control circuit of the A test signal is taken from the audio recording device, which is connected, for example, to the headphone jack of the audio recording device. The connected line is routed to the answering device and here certain control functions are required for the commissioning of the device. triggers. With a properly connected recording device and therefore the presence of test signals, the device switched to operational readiness. However, this arrangement has the disadvantage that, in addition to the special control circuit in the recording device, it also requires a An additional connecting line between the answering and recording device is required, so that in addition to the connecting lines and connections For operating voltage and audio transmission, an additional cable connection is required for the transmission of test signals. Furthermore, a A special recording device is required, namely a device with a headphone jack. This significantly increases the purchase price of the device. increased and additionally increased the sources of operational errors. The object of the present invention is to avoid these disadvantages and to create a reliable device using simple means, which The answering device can only be put into operation if the recording device is connected in accordance with regulations. This problem is solved according to the invention by providing the call circuit of the answering machine with an electronic device forming the unit. is assigned a switch which depends on the situation when the audio recording device is connected or not connected. different resistance states at the connection points for the audio recording device, the connection between the telephone exchange loop and maintains or interrupts the call loop. In this way, it is possible to control the connection between the answering machine and the to manufacture a recording device with only a few wires and to use any commercially available device as a recording device — even a simple cassette recorder — to use. In the preferred embodiment of the invention, the electronic switch is formed by at least one transistor, which at Blocking the call circle for recording devices that are not connected According to a further feature of the invention, the power and audio supply from the answering device to the recording device is via a single Connecting cable. This arrangement provides optimal coupling between the two devices and contributes in a particularly advantageous way to a simple and reliable operation of the device. The following description explains an embodiment of the invention with reference to a drawing. In the circuit diagram shown, the telephone answering machine is indicated by 10. It has a power supply 12 and a call circuit 14. About The power supply unit 12 of the device 10 is connected to the mains via terminal 16. The mains voltage, for example 220 V, is supplied to the power supply unit. 12 reduced to an operating voltage of approximately 7 V and connected via lines 18, 18a and 20 to a recording device 22 separate from the device 10, e.g. tape recorder, of known type laid The line connection between the separate units 10 and 22 is provided by a pluggable cable 24. A second connection 26 connects the telephone loop (a / b) via a switch 28, a resistor R 1 and a line 30 to the Call circuit 14. Another line 32, assigned to switch 28, leads to the audio pickup S in the recording device 22, for which cable 24 provides a third The conducting artery has Lin, a transistor T serving as an electronic switch with resistors R2, R> and Ra acting as voltage dividers, is in the manner shown. assigned to lines 18, 18a and 20. Line 18 can also be directly connected to line 18a via a contact M. If the recording device 22 is accidentally not connected correctly, i.e., if cable 24 is not plugged in and / or the If device 22 is not switched on via its main switch, the connection between lines 18a and 20 remains open. The current flows (with contact M currently open) through resistors R2 and R) to the base of transistor T, making it conductive. The ringing signals arriving from the exchange line via switch 28 therefore do not reach line 30 leading to call circuit 14, but are instead diverted via the collector-emitter junction of transistor T.