Spy World - Your One-Stop Surveillance Shop - surv audio

By: Spy World  12-08-2011

There are several methods used to 'listen in' to a room. A popular method is to fit a microphone in the area, e.g. in the ceiling or another convenient place in the room and run wires back to the LP, (listening post) at a convenient place in the building.
It is not possible to just fit a microphone and run a length of cable back to the listening post, the signal from the microphone will be reduced and become noisy if the cable is too long. A special amplifier is connected to the microphone allowing a long length of cable to be used back to the listening post.
Normally, such systems need to have four wires, two for power and two to carry the audio signal.
Our audio room monitor only needs two wires which carry the audio from the microphone amplifier back to the listening post, and also carry power back to the microphone.
This system is known as the TWO-WIRE room listener.

Another popular method of listening into a room, is to use a special module connected across the telephone line in the room to be monitored. After fitting this module across the phone line, all room conversations can be listened to by connecting the main amplifier across the phone line at some other place.


This is the module with attached microphone to be fitted in the room to be listened to.


Whilst a duplicate copy of a tape is often needed, e.g. a duplicate tape of telephone conversations, it is not possible to copy a tape by simply connecting the headphone output of one tape deck to the microphone input of another recorder.

It is possible to duplicate a tape using two standard cassette recorders after fitting the COPYING ADAPTOR between the headphone output of one machine and the mic input of another.

A headphone socket on the copying adaptor allows you to listen to the tape whilst making the copy.

RADIO TRANSMITTERS (BUGS)A 'BUG' is a radio transmitter that can be left in a room allowing the user to listen into room conversations by tuning into the 'bug' with a radio receiver. This bug can be received on a normal fm radio.
Line of sight range is about 400m, and battery life is around 48hours. FM BUG, - RT1

For secure 'bugging', it is not advisable to use transmitters that can be picked up with a normal fm radio.

For more 'professional' applications a bug with a matching radio receiver is used.


is a transmitter and receiver combination operating outside the normal fm radio band. The receiver and transmitter operate on a fixed frequency, no tuning is necessary as the receiver is matched to the transmitter, i.e. the TX33 can only be received by using the UX33 receiver.

Line of sight range is 150-200m.

UHF BUG, -TX33/UX33 Transmitter/Receiver pair


is also a telephone transmitter system, but the receiver is built inside a tape recorder, making it simpler to use.

The transmitter is attached to the line and the recorder is placed within range. The recorder is put onto record but will only start recording when the phone is used, and switch off automatically when the phone is put down.


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