Posted by Circuits Arena on Friday, 22 April 2016
Home Telephone Call Recorder Circuit Diagram is the artlcle explaining Home Telephone Call Recorder Circuit Diagram This is the circuit connection of the home telephone call recorder that uses very few com...
Home Telephone Call Recorder Circuit Diagram
This is the circuit connection of the home telephone call recorder that uses very few components. In order to understand its working, we must first have the basic knowledge of standard telephone wiring and a stereo plug. In some countries, landline telephones primarily use RJ11 wiring,
which has two wires tip and ring. While the tip is the positive wire, the ring
is the negative one. And together they complete the telephone circuit.
In a telephone line, voltage between tip and ring is around 48V DC when the handset is on the cradle (idle line). In order to ring the phone for an
incoming call, a 20Hz AC current of around 90V is superimposed over the
DC voltage already presents in the idle line.
The negative wire from the phone line goes to IN1, while the positive wire goes to IN2. Further, the negative wire from OUT1 and the positive wire from OUT2 is connected to the phone. All the resistors used are
0.25W carbon film resistors and all the capacitors used are rated for
250V or more. The negative terminal of “To AUX IN” is connected to pin 1
of the stereo jack while the positive terminal is connected to pins 2
and 3 of the stereo jack. This stereo jack, in turn, is connected to the
AUX IN / Audio Input of any recording device, such as a computer, audio cassette player, CD player, DVD player, etc. In this case, we will use a
computer desktop/notebook to make a call record.
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.
