A Synopsis

On

Telephone Conversation Recorder

Submitted in Partial Fulfillment for the Degree of Bachelorin

Electronics and Communication

Introduction

Today telephone has become an integral part of our lives. It is the most

widely used communication device in the world. Owing to its immense

popularity and widespread use, there arises a need for call recording

devices, which find application in call centers, stock broking firms, police,

offices, homes, etc. A cassette tape phone recorder is the easiest phone recording device

available. Any telephone conversation can become the source of critical information for personal

or business use. These telephone recorders use cassette tapes to record phone calls to have

definitive proof of a conversation. It is an advantage that if you operate a business with several

customer service representatives, you may have a need to record the phone conversations of

those employees. Automatic telephone conversation recorder makes use of a relay and a tape

recorder so as to record a conversation.

Block Diagram

The following block diagram shows an automatic telephone conversion recorder which gets

switched on as soon as the handset is being lifted. The tape recorder gets switched OFF when the

handset is replaced. The signal is suitably adjusted to a level at which they can be recorded using

the “MIC-IN” socket of the tape recorder.

Connections X1 and X2 in the circuit are connected to the telephone lines. The values of R1 and

R2 may be changed depending on the input impedance of the tape recorder's “MIC-IN”

terminals. The second part of the circuit controls relay RL1, which is used to switch ON/OFF the

tape recorder.

Circuit Diagram

Connections X1 and X2 in the circuit are connected to the telephone lines. Resistors R1, R2 and

VR1 act as a voltage divider. The voltage appearing across R2 and VR1 is fed to the “MICIN”

socket of the tape recorder. The values of R1 and R2 may be changed depending on the input

impedance of the tape recorder's “MIC-IN” terminals. Capacitor C2 is used for blocking the flow

of DC. The second part of the circuit controls relay RL1, which is used to switch ON/OFF the

tape recorder. A voltage of 48 volts appears across the telephone lines in on-hook condition. This

voltage drops to about 9 volts when the handset is lifted. Diodes D3 through D6 constitute a

bridge rectifier. This ensures that transistor T1 gets voltage of proper polarity, irrespective of the

polarity of the telephone lines. During on-hook condition, the output from the bridge (approx.

48V DC) passes through 12V zener D7 and is applied to the base of transistor T1 via the voltage

divider comprising resistors R3 and R4. This switches on transistor T1 and its collector is pulled

low. This, in turn, causes transistor T2 to cut off and relay RL1 is not energised. When the

telephone handset is lifted, the voltage across points X1 and X2 falls below 12 volts and so zener

diode D7 does not conduct. As a result, base of transistor T1 is pulled to ground potential via

resistor R4 and thus is cut off. Thus, base of transistor T2 gets forward biased via resistor R5,

which results in the energisation of relay RL1. The tape recorder is switched ON and recording

begins. The tape recorder should be kept loaded with a cassette and the record button of the tape

recorder should remain pressed to enable it to record the conversation as soon as the handset is

lifted. Capacitor C3 ensures that the relay is not switched on-and off repeatedly when a number

is being dialed in pulse dialing mode.

Applications

There are four fundamental reasons why an organization may wish to Record Phone Calls: 

Improve customer service 

Record transactions of value 

Comply with industry regulations 

Increase security & avoid abuse 

Advantages

It improves customer service by increasing the effectiveness in dealing with customers

thus in turn improving revenue, margin and profits.

It helps in documentation of verbal negotiations and decisions which plays a vital role in

case of dispute resolution and confirmations.

It also plays an important role in Increase Security & Avoid Abuse

Get second opinions on conversational ambiguities

Meet compliance obligations

Evaluate your team's phone call performance

References

[1] http://www.electronicsmaker.com

[2] http://www.usbcallrecord.com

[3] http://www.telephonecallrecorder.com