Glossary

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Term	Definition
66 Block	A terminal block used for the interconnection of telephone wiring. Also known as a “punch down block” or “split block”.
“A” Battery	A term used to describe a filtered talk battery or supply. This is generally used as the power source for the audio portion of an electronic device. “A” battery may be substituted for “B” battery, but “B” battery may never be substituted for “A” battery. Compare: B battery.
Air Plenum	Air space above drop ceiling tiles used for air return. Usually requires special wiring or conduit to meet local fire code specifications.
Alert Tone	Alert tone which may precede a voice announcement from a paging zone. Alert tones are primarily used in talkback paging systems in order to discourage unannounced monitoring of zones.
All Call	A feature of a zone paging system which allows the user to a dial a specific code and by doing so, access all of the speakers associated with that system. If the zone paging system features a talkback capability, the talkback signal is inhibited during all call access.
Ambient Noise	Background noise in an area.
Amphenol	A 50 connection terminal conductor connector commonly used for telephone equipment and overhead paging systems.
Amplifier	An electronic device used to increase signal power or amplitude.
Antiblast Control	An automatic potentiometer. This device monitors the ambient noise level and adjusts the audio output of paging speakers or horns accordingly when inserted between the one-way page control and the audio input to the speakers. (a.k.a. Automatic Volume Control)
Attenuation	Reduction in magnitude of any electrical parameter of a signal, on passing along any transmission path.
Audio Frequency	Frequencies detected by the human ear, usually between 20 and 20,000Hz.
Automatic Gain	A device for holding the output volume of a audio source substantially constant control despite variations in the input signal.
“B” Battery	A term used to signify a signal battery or supply. Generally a “B” battery’s filtering is not as refined as an “A” battery’s, this source is usually utilized to power the relays in an electronic device. Should not be used for page control units in most cases. Compare: “A” Battery
Backbox	Speaker housing or enclosure designed to provide coverage for the rear of a ceiling speaker. This coverage maybe required by local building codes for air plenum type ceilings or may be used in other type ceilings to protect the speaker from dust and debris accumulation.
Bandwidth	The range of signal frequencies that a circuit or network will respond to or pass.
Battery Backup	An alternate power source that is used in the event of a loss of a system’s primary power.
Battery Feed (BF)	A circuit utilized to provide talk battery as well as audio coupling in a telephone system. It is generally provided by applying a potential difference between two halves of a split coil (repeat coil).
BGM	Abbreviation for Background Music.
Bridge	An optional hardware device utilized for ceiling speaker support. It is generally placed in a drop type ceiling so that the frame of the bridge rest on the support grid system thereby alleviating any stress to the ceiling tile itself.
Bridging Clips	Metallic clips used for connecting the two halves of a split punch down block.
Butt Set	A self-contained test telephone primarily used for telephone installation trouble-shooting. Used to listen to audio signals and provide telephone access to paging systems.
Central Office (C.O.)	The switching equipment that provides local exchange telephone service for a given geographical area, designed by the first three digits of a telephone number. The main distribution center for telephone service to a particular area. In addition to basic telephone switching, C.O.s may also provide Centrex or Essx service and direct inward dial (DID) service.
C.O. Line Position	A key system or PBX (PABX) C.O. line circuit which can be used to access most Valcom Page Control Interface Units.
Centrally Amplified System	An old fashion type of public address system which utilizes central amplifiers.
Centrex	Service provided through the C.O., which provides the end user with many or all of the features of a PBX without the expense or upkeep of a private switch. The service is purchased from the C.O. and requires no “on premises” equipment.
Closed Loop	DC load applied across tip & ring which completes the circuit and allows loop current to flow. This state indicates a request for service from the control unit, station port or central office.
Combination Paging	A paging system in which a handsfree page control unit is used in conjunction with both talkback and one-way speakers. (a.k.a. mixed paging)
Common Battery	A system of supplying direct current for the telephone set from the C.O> (a.k.a. Talk Battery)
Contact Closure	A device, such as a relay or pushbutton, which provides a short circuit upon activation. Closures are used to activate various features on page controls as well as to activate certain controllers during page port access.
Control Unit	With respect to paging systems, a control unit provides the interface to the telephone system and may also provide various features.
Crosstalk	Undesired voice-band energy transfer from one circuit or conductor to another (usually adjacent).
Daisy Chaining Cable	Wiring multiple devices on one continuous wire run. Compare: Home Run
Dial Tone	The tone that is heard by the caller when a multi-zone page control is first accessed.
Distributed Amplified System	The modern way to integrate public address announcements with a telephone system in which each speaker has a built-in amplifier and volume control, (a.k.a. the Valcom System). Compare: Centrally Amplified System
Dry Contact Closure	A switchable set of contacts with no potential difference between them or to any other reference point.
Dual-Tone Multi-Frequency	Use of two simultaneous voice band tones for signaling or dialing on a telephone keypad. (DTMF)
Electric Strikeplate	An electro-mechanical door lock.
Equalizer (EQ)	A device that modifies an audio signal through the use of multiple adjustable filters.
Extention Port	A port on a telephone system that is intended for connection to a system telephone or station level paging adapters.
Federal Communications Commission (FCC)	A government agency that regulates and monitors the domestic use of the electromagnetic spectrum for communications.
Feedback	The process of returning a fraction of the output energy of an energy converting device to the input. The circuit that transmits the feedback signal to the input is the beta circuit; the circuit containing the active device, which generates the output signal, is the mu circuit.
Frequency	The rate in hertz (cycles per second) at which a signal pattern is repeated.
Frequency Response	A measure of the effectiveness with which a circuit, device or system transmits the different frequencies applied to it. The way in which an electronic device (mic, amp or speaker) responds to signals having a varying frequency. This is a measurement of how well an amplifier reproduces and amplifies a specified audible range with equal amplitude or intensity.
FXO	Foreign Exchange Office. (see also C.O. Line Position, trunk)
FXS	Foreign Exchange Subscriber (see also Extension Port, Station Port)
Ground	An electrical connection to the earth or to a common conductor which is at a reference potential that serves as a reference point for all other potentials in the circuit.
Ground Start	With ground start signaling, a telephone immediately upon entering an offhook state, requests service from the C.O. by applying a ground to the ring lead of the tip and ring pair. The C.O. responds and indicates preparation to receive digits, by placing a ground on the tip lead of the tip and ring pair.
Group Call	The ability to page a specific combination of zones within a multi-zone paging system.
Half-duplex	A circuit that carries information in both directions, but only in one direction at a time.
Head End Equipment	The portion of a paging or telephone installation at which all of the system components originate.
Hertz (Hz)	A unit of measurement used to indicate the frequency of sound or an electrical waveform.
Home Run	The practice of providing a dedicated wire run to each speaker in a PA system. Compare: Daisy Chaining Cable
Impedance	A measure of the response of an electric circuit to an alternating current. The current is opposed by the capacitance and inductance of the circuit in addition to the resistance.
Inhibit	A feature on certain page controls which cancels or inhibits the paging speaker audio whenever two phones are offhook on the page control’s tip and ring. This feature is activated when each of the telephones provided an “A lead” ground to 10k resistors which are common to the inhibit terminal.
Intermediate Distribution Frame (IDF)	An extension of the main distribution frame (MDF). The IDF, usually at some distance from the MDF, is the location where subelements of the telephone or paging system are distributed to a particular area of an installation.
Loop Start	The usual method of signaling an offhook or line seizure, where one end closes the loop and the resulting current flow is detected by a switch at the other end. With loop start, the telephone upon entering an offhook state, draws loop current from the C.O. thereby signaling that service is being requested.
Loss	Attenuation of a signal from any cause.
Main Distribution Frame (MDF)	The location in a telephone or paging installation where all of the elements which comprise that system originate and/or interface with the public telephone network.
Meet Me Page	A feature where following a general page, the paged party may dial a code at an extension telephone and by doing so, secure a private talkpath to the paging party and subsequently, free the page path for additional use.
Nightring	A feature which provide either by a telephone system, a page control or a peripheral common audible ringing device. Nightringing provides a signal, usually over the paging system, to indicate that a telephone line is in a ringing state.
Non-polarized	Not sensitive to the applied signal’s polarity.
Off-hook	The condition that indicates the active state of a customer telephone circuit.
Off Premise Extension (OPX)	A phone extension located in a different building from common equipment.
One-way Paging	Public address announcement with out the benefit of hearing response from the paged area.
Override Tip & Ring	This feature is usually accessed through a separate tip and ring input and allows any audio input from this tip and ring to override all other pages in progress. Override tip and ring does not necessarily provide automatic access to an all call.
Page Control Lead (PC)	An output terminal on select page control units that is connected internally through a N.O. relay to system ground. Whenever the page control is accessed, the page control terminal is switched to ground potential. This terminal is useful for providing ground to external relays.
PABX or PBX	A private (automatic) branch exchange is a telephone system that provides telephone switching services within business or private establishment. PBX’s provide 2 or 3 digit access from station to station as well as many other features. The telephone terminals used with a PBX are generally of the industry standard type.
Page Port	An audio output provided by a telephone system. Usually the page port is accessed by dialing a code or selecting a dedicated line key.
Parallel Connection	Connection of system elements such that like connection points are common.
Phantom Zone	This term is used to describe a “non-background music” zone output on a single zone page control. Single zone page controls, which provide a phantom zone, will always have dual speaker outputs, one with BGM and one without BGM.
Pinout	The physical pattern of connection points for a device.
Plain Old Telephone Service (POTS)	Single line residential rotary dial service. Quite often a 500 (rotary desk) or 2500 (touch tone desk) telephone may be referred to as a “POTS telephone”.
Potentiometer	A variable resistor. A movable sliding contact is used to vary the potentiometer’s resistance.
Relay	An electromechanical device comprised of a coil and various sets of contacts (determined by the relay selected). When a voltage is applied to the coil, a magnetic field is induced around the coil. The magnetic field attracts metallic, movable contacts and creates either a closed contact or an open contact or various combinations.
Repeat Alert Tone	A tone heard through a talkback speaker every 15 seconds to prevent eavesdropping.
Ring	The alerting signal to the subscriber or terminal equipment; the name of the one conductor of a telephone wire pair, designated by R.
Ring Voltage	Voltage that is applied to a telephone or telephone system in order to signal an incoming telephone call.
Ringback Tone (RBT)	In telephony, it is a progress tone heard by the calling party, which indicates that signaling (ringing) is being provided to the called party.
Ringer	A device that produces audible signaling in response to ring voltage or contact closure.
RTHF	Rotary Tone Handsfree
RTVA	Rotary Tone Voice Announce
Series Connection	Circuit elements that are connected so that current flows through each of them.
Side Tone	The portion of the talker’s voice which is fed back to his receiver.
Signal Battery	See B Battery.
Sound Reinforcement	Amplification of a line of site speaker’s voice.
Stand Alone System	A system that does not require the support of subsequent system(s).
Splash Tone	A tone that immediately precedes a voice announcement on handsfree talkback systems (prevents eavesdropping).
Station Level	Access Indicates that the paging equipment will be accessed via an incoming phone line or station port rather than through a KSU or PBX page port or trunk port. Users must dial an extension number or telephone number in order to execute a page.
Station Port	An output on a KSU or a PBX where the actual telephone terminal is connected.
Strikeplate	See Electric Strikeplate.
Subscriber	The telephone service customer.
Switch	A generic term for a KSU or PBX.
Talk Battery	See A Battery.
Talkback	A type of paging system in which individuals in the paged area can respond through the paging speakers of horns.
Time Clock Tone	A single tone broadcast through the paging system when a time clock controlled dry contact closure is applied to an appropriate signaling device.
Tip	One conductor of a telephone wire pair, designated by T; usually the more positive of the two.
Tip & Ring	The terms used to identify single pair telephone station wiring. The tip conductor usually has a positive potential with respect to the ring conductor.
Trunk	A transmission channel connecting two switching machines.
Trunk Port	The point of connection on a telephone system where the central office lines or trunk lines, are usually connected.
UPS	Uninterruptible Power Supply.
Valcom Power Unit (VPU)	One Valcom power unit is equal to and defined as, 50mA @ 24VDC. Valcom power units were devised in order to aid in the determination of total system power required when configuring a Valcom paging system.
Voice-grade Line	A local loop or trunk, having a bandpass of approximately 300 – 3,000Hz.
Voice Operated Switching (VOX)	Provides the ability to activate a device simply by the presence of a specific level of audio signal.
Voltage	A measure of the electrical force that causes current flow in a circuit.
VSP	Valcom System Practice. Term used for a Valcom Installation Manual.
XLR Connector	A connector usually utilized for the connection of a microphone to its associated cable. The pin count of an XLR connector may vary from three to seven pins.