Share a home telephone recorder circuit diagram

This is the circuit connection of a home telephone recorder using very few components. In order to understand how it works, we must first have a basic knowledge of standard telephone wiring and stereo plugs. In some countries, landline phones mainly use RJ11 wiring, which has two wires ? ? "tip and ring. While the tip is the positive wire, the ring is the negative wire. Together they complete the telephone line. In the telephone line, when the handset is placed on the cradle (idle line), the voltage between the tip and the ring is about 48VDC. In order to make the phone ring to answer the incoming call, an AC current of about 90V of 20Hz is superimposed on the DC voltage already present in the idle line.

The negative terminal of the telephone line is connected to IN1 and the positive terminal is connected to IN2. In addition, the negative line from OUT1 and the positive line from OUT2 are connected to the telephone. The resistors used are all 0.25W carbon film resistors and the capacitors used are all above 250V. The negative terminal of "ToAUXIN" is connected to pin 1 of the stereo jack and the positive terminal is connected to pins 2 and 3 of the stereo jack. This stereo jack in turn is connected to the AUXIN/AudioInput of any recording device such as a computer, cassette player, CD player, DVD player, etc. In this case, we will use a computer desktop/laptop to record the calls.

When a call comes in, an AC current of about 90V at 20Hz is superimposed on the DC voltage already present in the idle line. This current is converted to DC by the diode and fed into resistor R1, which reduces its amplitude and feeds it into LED1. The current is further reduced in amplitude by resistor R2 and fed into the left and right channels of the stereo jack, which are connected to the AUXIN/AudioIn port of the computer, which in most notebook devices is the same between the Audio input/microphone input.

Any recording software can be used to record home phone calls, such as AVS Audio Editor, Audacity Audio Recorder, or Audio Recorder for Free. When a call comes in, you need to launch the recording software and start recording.

For phone call recording, just connect the stereo jack to the "Audio In" or "Mic In" port of your PC/Laptop. Install the audio recorder software on your PC/Laptop. Run the software and check the settings to make sure the input is correct. Now you can record any call. When a call comes in, press the record key on the software and pick up the handset to answer the call. Press the stop button after the call ends and save the file in the desired location. Each software may have different settings, you can read the manual of each software to learn how to record audio.

If you want to change the output volume, you can change the value of resistor R2. You can use a variable resistor in series with R2 to change the output volume of the home phone recorder circuit. The recorded audio clip can be edited using different options in the AudioRecorder software.

You can build the circuit on a general purpose PCB and enclose it in a small box. Use RJ11 connector and stereo jack to connect the telephone set and computer desktop/laptop (for call recording). The telephone cable can be used to connect the telephone line and the home phone recording circuit. It is recommended to use a shielded cable to reduce interference in the recording so that we get good audio performance from the recording. These interferences can also be reduced by increasing the value of R2 to about 15K.