Bug -A hidden microphone, usually connected to a radio transmitter. Also, may be wired directly to a listening post.

Bumper Beeper - A radio transmitter which is attached to a vehicle for use as a beacon or homing device for tailing.

Carrier Current Device - Transmits a signal, modulated by audio, along a pair of wires (electrical or phone line) to a compatible receiver. The signal travels along the wires with very little radiated from the lines.

Contact Mic - A microphone that picks up sounds by amplifying vibrations from a solid surface such as a door, window or wall.

Harmonics - Multiples of a basic frequency. Their presence indicates a clandestine transmitter.

Hookswitch Bypass - A modification to the telephone instrument so that room sounds are picked up and passed down the phone line to a listening post even with the telephone handset hung up. Turns the telephone into a room bug.

Hot mic - See Hookswitch Bypass.

Jammer - A device that produces noise in hidden microphones, so that conversations are unintelligible to the listener.

Mail Cover - Interception of mail by the Post Office for a government agency.

Parallel Tap - Connected across both wires of a telephone line. Usually used to activate a tape recorder. DC resistance ranges from 10 megohms to 35 megohms. May also be a radio transmitter, in which case, a separate battery is required for powering the transmitter.

Parasitic Device - A type of eavesdropping device that pirates its operating power from a source such as the telephone line or house wiring. It requires no battery of its own.

Series Tap - Usually a radio transmitter. It obtains its power from the telephone line to which it is attached. It is installed in series (in line with one wire). Generally has a DC resistance of 70 to 300 ohms. Can also be used to activate a tape recorder.

Spike Mic - Similar to a contact microphone, but has a metal spike that is driven into a wall, etc. to pick up voice vibrations.

Tap - See Wiretap.

Wired Mic - An installation where a microphone is connected to a listening post by a pair of wires.

Wiretap - Clandestine interception of a telephone conversation. Operates when the phone is in use.