Home Telephone Call Recorder Wiring Diagram
When a call comes in, around 90V AC current at 20Hz is superimposed over the DC voltage already present in the idle line. This current is converted into DC by the diodes and fed to resistor R1, which reduces its magnitude and feeds it to LED1. The current is further reduced in magnitude by the resistor R2 and fed to the right and left channels of the stereo jack, which are connected to the AUX IN / Audio In port of a computer, in most of notebook devices, it is same between Audio Input / Mic Input.
You can built the circuit on a general-purpose PCB and enclose it in a small box. Use an RJ11 connector and stereo jack for connecting the telephone set and computer desktop/laptop (for call recording). Telephone cords can be used to connect to the phone line and the home telephone call recorder circuit. Use of a shielded cable is recommended to reduce disturbances in the recording so it we will get good audio performance from the recording. These disturbances can also be reduced by increasing the value of R2 to about 15K.