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

3) 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. 

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

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

6) 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. 

7) Hot mic - See Hookswitch Bypass. 

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

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

10) 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. 

11) 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. 

12) 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. 

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

14) Tap - See Wiretap. 

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

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