Glossary of Terms Common in TSCM

These few definitions are provided to give you a brief and simple explanation of some terms commonly used by TSCM professionals. These definitions are not designed to be all-inclusive and are written in layman's terminology.

ALTERNATING CURRENT (A/C)
An alternating current is one whose amplitude of current flow periodically rises from zero to a maximum in one direction, decreases to zero, changes its direction, rises to a maximum in the opposite direction, and decreases to zero again.

AMPLITUDE MODULATION (A.M.)
A method of impressing audio signals on a radio carrier signal by varying the strength (amplitude) of the carrier.

ACCESS AREA
The area of vulnerability to intercept between a telephone subscriber and the serving central office.

AGENT TRANSMITTER
A small radio transmitter concealed on a person's body used for agent or informer protection or consensual monitoring.

AMPLIFIER
An electrical circuit that makes a small signal larger by increasing its voltage or power level.

ANTENNA
A conductor or system of conduction for transmitting or receiving radio signals.

APPEARANCE POINT
A location where metallic access is readily available to a given telephone line pair.

AUDIO
Sound waves audible to the human ear.

AUDIO FREQUENCY
That range of frequencies the human ear can detect which is from about 15 to 20,000 Hertz. Only those from 300 to 3,000 Hertz are transmitted through the telephone.

BANDWIDTH
A specification describing the highest and lowest frequencies an amplifier can handle with no loss beyond that stipulated.

BATTERY
A large group of individual electrical cells.

BROAD BAND-PASS RECEIVER
A receiver designed to demodulate received AM, or FM signals indiscriminately over a wide frequency range all at one time.

BUG
A clandestine listening device; generally a small, hidden microphone and radio transmitter.

BUGGING
The process of monitoring conversations by electronic means.

BYPASS
The alteration of a telephone instrument so that it will pass audio even with the handset on the cradle (an alteration to the hookswitch).

CARBON MICROPHONE
A microphone which depends, for its operation, on the variation in resistance of carbon granules.

CAPACITOR
A device consisting essentially of two conductive surfaces separated by a dielectric.

CARRIER
A term broadly used to designate a single RF frequency upon which audio signals can be impressed.

CARRIER CURRENT TRANSMITTER
A device which is powered by and also transmits intelligence on to the line it is attached to. The signal is received by a receiver attached to the same line.

CENTER OF CONVERSATION
An imaginary point midway between conversationalists. A point for potential microphone placement.

CENTRAL OFFICE
The telephone company switching equipment that provides local exchange telephone service for a given area, designated by the first three digits of the telephone number. The telephone equipment housing for a specific geographical area.

CONDENSER MICROPHONE
A charged microphone which depends, for its operation, on the variation in capacitance of its plates.

CONTACT MICROPHONE
A specially constructed microphone designed to be attached directly to the surface to be monitored. This type of microphone generally responds only when the object or surface is vibrated.

CROSS CONNECT CABINET
The cabinet which houses the wiring that cross connects the feeder cable conductors with the distribution cable conductors.

CRYSTAL MICROPHONE
A microphone that depends for its operation on the generation of an electric charge by the deformation of a crystal.

DEMODULATION
The process of sensing variations in a radio frequency carrier and reconstructing the original modulating audio signal from them.

DIGITAL
Any information in discrete form using a binary number system.

DIRECT INWARD DIAL (DID)
A feature on PBX's which enables incoming calls to be routed directly to selected stations without attendant assistance.

DIRECT INWARD SYSTEM ACCESS (DISA)
A feature on PBX's which allows an external caller access to the PBX and all of its features such as tie and watts lines by dialing in on the DISA trunk.

DROP-IN
A series wiretap that is built on the back of a telephone handset's carbon microphone.

DYNAMIC MICROPHONE
Any of several microphone types in which the coil is attached to the diaphragm and surrounded by a magnetic field from a permanent magnet.

ELECTRONIC SWITCHING SYSTEM (ESS)
A computer-controlled voice and/or data switch.

EARPIECE
A small, electro-magnetic speaker for use in a telephone handset.

ELECTRET MICROPHONE
A permanently charged condenser microphone which has an extremely low mass diaphragm.

EXCHANGE AREA
The area within which telephone service is provided without extra charge per call. Same as local calling area.

FIELD STRENGTH METER
An instrument used to give relative measurements of the radiation fields close to an operating transmitter.

FREQUENCY MODULATION
A system of impressing audio signals onto an RF carrier by causing them to make slight alterations in its frequency.

FREQUENCY DIVISION MULTIPLEXING (FDM)
A technique in which the available transmission bandwidth of a circuit is divided by frequency into narrower bands, each used for a separate channel.

HAND SET
The part of the telephone instrument used for talking and listening.

HARMONICA BUG
See infinity transmitter

HARD WIRE
Use of wire conductors rather than a radio transmitter to communicate information between two points.

HOOKSWITCH
Switch contacts inside the telephone which remove the telephone from the line circuit when the handset is on-hook.

HERTZ
A measurement unit of frequency equal to one cycle per second.

IMPEDANCE
The total opposition to current flow presented by a component or a circuit. This may include any or all of the principles of INDUCTANCE, CAPACITANCE, or RESISTANCE.

INDUCTOR
A device consisting of a coil of wire. This core may be soft iron or air. An inductor opposes the flow of AC and variations in the flow of DC.

INDUCTION COIL
To isolate the receiver from the direct current that is present on the central office line and to increase the operating efficiency of the telephone.

INFINITY TRANSMITTER
A transmitter designed for installation inside a telephone instrument. This device is a tone activated hookswitch bypass device which upon activation answers the call before the phone can ring and then transmits audio received from the carbon microphone. Variation exist which are designed to be used on the telephone line independent of a telephone instrument.

INTELLIGIBILITY
The quality, especially tape recorded speech, of being understandable in the sense that each individual word can be heard and recognized by a listener with normal hearing.

INTERCEPT
The aural acquisition of the contents of any wire or oral communication through the use of any electronic, mechanical or other device.

INTERMEDIATE FREQUENCY (IF)
In receivers, that frequency to which a selected incoming signal is converted by heterodyne with the local oscillator signal to which the remaining circuits of the receiver can be precisely tuned regardless of the frequency of the desired incoming signal.

LINE CARRIER CURRENT
A transmitter designed to send RF signals down a wire rather than radiating them into space from an antenna.

LISTENING POST
The site at which radio signals are received or wired microphone lines terminated for the purpose of monitoring and/or recording intercepted communications.

LOCAL LOOP
The pair of wires connecting a subscriber to the central office.

LOCAL OSCILLATOR
An oscillator used to produce a sum or difference frequency which will heterodyne with a desired incoming signal frequency to produce the intermediate frequency of a radio receiver.

MAIN DISTRIBUTION FRAME (M.D.F.)
The cross-connect frame at the C.O. or PBX where all the system pairs are connected.

MAGNETIC FIELD
The invisible lines of force which surround a magnetic object. The space in which these lines of force exist.

MAGNETIC MICROPHONE
A microphone which uses variations in the reluctance of a magnetic circuit as its operating principle.

MINI-TAP
A simple form of capacitively isolated tap whereby one capacitor is attached to each side of the pair.

MODULATION
The process by which audio signals are impressed on an RF carrier.

MULTIPLE
A multiple is a parallel connection of the subscriber's line on a branch feeder, typically seen in older cable distribution schemes.

NON-LINEAR JUNCTION DETECTOR
A special radio frequency transmitter and receiver with an antenna used to find non-linear junctions or diodes, transistors, etc.

NARROW BAND FM
FM radio which deviates no more than + 5 KHz as a result of modulation.

OFF HOOK
In telephone systems, an instrument with the handset lifted from its cradle.

ON HOOK
In telephone systems, an instrument with the handset hung up.

O.P.X.
Off premise extension.

PRIVATE AUTOMATED BRANCH EXCHANGE (PABX)
See PRIVATE BRANCH EXCHANGE

PRIVATE BRANCH EXCHANGE (PBX)
A term used synonymously with Electronic Private Automated Branch Exchange (EPABX) and Private Automated Branch Exchange (PABX). Similar to a central office exchange but smaller. A central off exchange can accommodate 10,000 subscribers. PBX systems are typically designed to accommodate from 20 to 10,000 subscribers or station. See CENTRAL OFFICE.

PANORAMIC DISPLAY
A device designed to display all signals present in a given frequency band as vertical pulses on a horizontal trace.

PARALLEL RF TAP
Radio frequency tap transmitter which is attached across both wires of a telephone line.

PARASITIC DEVICE
A series radio frequency wiretap that frequently uses the telephone line for an antenna. (Also known as a leach.)

PBX TRUNK
A circuit which connects the PBX to the local telephone company's switching center.

PEDESTAL
A splice case for feeder and distribution cables. Pedestals are also used as distribution terminals.

PIN HOLE
An air passage to a concealed microphone made with a needle or miniature twist drill. The microphone must be sealed air tight at the inner end of the passage in order to pick up sounds properly from the other end.

PREMISES
This is the space occupied by the customer.

QUICK PLANT
An audio bugging transmitter easily installed or dropped in target area.

RADIO FREQUENCY (RF)
Electro-magnetic waves used in radio communications to carry information.

READY ACCESS TERMINAL
A distribution terminal commonly used with aerial cable. Frequently referred to as a boot.

RECEIVER
A radio signal reception and demodulation device.

REMOTE MAINTENANCE FACILITY (PORT)
A PBX feature which allows remote diagnosis and reprogramming of the system over standard telephone lines.

RESISTANCE
The opposition that a conductor offers to the flow of direct current. In alternating current circuits, resistance is the primary component of impedance.

SATELLITE CLOSET
A room used in larger buildings to cross-connect tie cables on a particular floor to the individual telephone systems.

SERIES RF TAP
Radio transmitter which usually obtains power from the telephone line to which it is attached and is installed in series or in line with one wire.

SPARE PAIR
In telephone systems, a pair of unused wires in a cable.

SPIKE MICROPHONE
See contact microphone.

SPLIT/RESPLIT
A cable pair in which one conductor of the pair is mismatched with one conductor of another pair (split) and then corrected at a different point in the cable (resplit), causing mutual inductance and as a result cross-talk.

TERMINAL BLOCK
Point at which individual telephone instruments are connected to the interior phone lines of a building.

TERMINAL BOX
Point at which telephone lines are spliced or connected to cable.

THIRD WIRE BYPASS
In telephone systems, a telephone bypass method in which one wire in the instrument mounting cord is used to gain direct access to either the carbon microphone or the dynamic earpiece.

TIE LINE
A dedicated telecommunications circuit between two points.

TIE TRUNK
A trunk between two branch exchange installations.

TIME DOMAIN REFLECTOMETER (TDR)
A piece of equipment which sends a radar pulse down a cable pair to detect an impedance mismatch or discontinuity.

TRANSDUCER
A device that changes electrical energy into mechanical energy and vice-versa (i.e., telephone receiver).

TRANSFORMER
A device that uses the principal of mutual induction to convert alternating current in the primary windings into alternating current with voltage and current of a different value in the secondary windings.

TRANSMITTER
The microphone of the telephone instrument. A device that radiates RF energy.

TRUNK LINE
The main cable originating at the central office.

VOLT
The basic unit of electrical energy.

WIRE TAP
Clandestine interception of a telephone conversation away from the target premises.