Technical Training Glossary

   A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

110 Block
A terminal block used for the compact interconnection of Unshielded Twisted Pair (UTP) wiring. 110 blocks are superior for maintaining the integrity of the twist in UTP, but require special tools for troubleshooting.

66 Block
A terminal block used for the interconnection of UTP wiring. Also known as a “punch down block” or “split block”.

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 used in talkback paging systems in order to discourage unannounced monitoring of zones. In one way systems, alert tones bring attention to the impending message.

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 measured in dBspl.

Amphenol
A 50 connection point conductor connector commonly used for telephone equipment and overhead paging systems.

Amplifier
An electronic device used to increase signal power or amplitude.

Atom Feed
Atom Syndication Format (ATOM Feed) is an XML language used for web feeds.

Attenuation
Reduction in magnitude of any electrical parameter of a signal, on passing along any transmission path. In public address systems, this is typically used to describe the reduction of audio level.

Audible 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 consistent despite variations in the input signal.

Automatic Volume Control (Antiblast Control)
An automatic potentiometer. This device monitors the ambient noise level and adjusts the audio output of paging speakers or horns accordingly. (a.k.a. Automatic Volume Control).

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. Commonly used in conjunction with a bridge.

Bandwidth
The range of signal frequencies (Hertz) that a circuit or network will effectively reproduce 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)
DC voltage present on POTS telephone lines used for signaling and for powering POTS telephones.

BGM
Abbreviation for Background Music. BGM is sublimely broadcast music within a facility.

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.

Bridging Clips
Metallic clips used for connecting the two halves of a split punch down block.

Browser Based Server
A network server that is accessed via a web browser thus making it accessible from any device capable of accessing websites.

Butt Set (Lineman’s Handset)
A self-contained test telephone primarily used for telephone installation troubleshooting. Used to listen to audio signals and provide telephone access to paging systems.

Call Button
A momentary switch used with talkback speakers to notify a recipient device (telephone) that a user is requesting two way communication from the talkback speaker location. The conversation is initiated when the recipient device answers the call.

Calling Party Control (CPC)
A signal sent from a phone system, or a telephone service provider, to the telephone subscriber's equipment to indicate that the calling party has hung up. This is typically accomplished via an Open Loop Disconnect where battery feed voltage is momentarily removed from the trunk.

Central Office (C.O.)
The switching equipment that provides local exchange telephone service for a given geographical area. 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 Port (Loop Start)
A key system or PBX (PABX) C.O. line circuit which can be used to access most Valcom Page Control Interface Units. C.O. line ports connect to dial tone sources.

Centrally Amplified System
An old fashioned type of public address system which utilizes central amplifiers.

Centrex (Hosted Telephone Service)
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 talkback capable page control unit is used in conjunction with both talkback and One-Way speakers. (a.k.a. mixed paging)

Common Alert Protocol
The Common Alerting Protocol (CAP) is a simple, general format for exchanging emergency alerts and warnings over data networks. CAP allows a consistent warning message to be disseminated simultaneously over many different warning systems, thus increasing warning effectiveness while simplifying the warning task.

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 (electromechanical switch) 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 analog paging systems, a control unit provides the interface to the telephone system and may also provide various features.

CPC
See Calling Party Control

Cross Connect
A device facilitating the termination of cables and their interconnection, and/or cross connection, typically by means of a patch cord or jumper.

Cross Connection (Interconnect)
Methods of using cross connect (either with or without a patch cord or jumper).

Crosstalk
Undesired voice-band audio transfer from one circuit or conductor to another (usually adjacent).

Daisy Chaining Cable
Wiring multiple devices on one continuous looped wire run. Compare: Home Run

dB (Decibel)
The decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, often power or intensity. One of these values is often a standard reference value, in which case the decibel is used to express the level of the other value relative to this reference.

dBspl
Sound pressures described in terms of dB (decibels)

Dial Tone
The tone that is heard by the caller when a multi-zone page control is first accessed.

Dispersion Angle
With regard to speakers and horns, this is the entire angle off axis at which the sound pressure diminished by 6 dBspl.

Distributed Self-Amplified System
The modern way to integrate analog 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 (DTMF)
Use of two simultaneous voice band tones for signaling or dialing on a telephone keypad.

Eavesdropping
The act of monitoring an area without knowledge or consent of the occupants.

Electric Strike plate
An electro-mechanical door lock.

Endpoint
In Valcom VoIP systems, the terms endpoint and gateway are used to describe the actual Valcom network connected equipment. In general, the term endpoint is used to describe devices that provide information to users without any interaction on the user’s part (speakers, horns, LED signs) where gateway is the term used to interface to support equipment (audio sources, telephones, relays, etc)

Equalizer (EQ)
A device that modifies an audio signal through the use of multiple adjustable filters.

Extension Port
A port on a telephone system that is intended for connection to a system telephone or station level paging adapters. See Station Port.
Federal Communications Commission (FCC)
A U.S. 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. In audio amplification systems, feedback results in an undesirable system wide squeal.

Feedback Elimination
A method of digitally delaying paging system announcements until the originating device is returned to an idle state. This breaks the feedback loop by delaying the announcement.

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 Port

Foreign Exchange Office - See C.O. Line Port

FXS Port

Foreign Exchange Subscriber - see also Extension Port, Station Port

Gateway
In Valcom VoIP systems, the terms endpoint and gateway are used to describe the actual Valcom network connected equipment. In general, the term endpoint is used to describe devices that provide information to users without any interaction on the user’s part (speakers, horns, LED signs) where gateway is the term used to interface to support equipment (audio sources, telephones, relays, etc)

Graphical User Interface (GUI)
A visually displayed method of allowing users to control a system or systems.

Granularity
The extent to which a system can be subdivided. In analog systems this is dictated by the number of audio outputs of the control equipment and the system cabling.

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 off hook 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
A grouped combination of zones within a multi-zone paging system used to direct announcements to a target audience without disrupting other areas.

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.

Hosted PBX
A VoIP based telephone system with no “on premise” telephone switch. Hosted PBXs are operated and maintained by a Voice-over-IP (VoIP) service provider.

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 off-hook 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 sub elements of the telephone or paging system are distributed to a particular area of an installation.

Line Level Audio
A pre-amplified, industry specific, audio signal level. Usually described in terms of dB or volts.

Loop Start
The usual method of signaling an off hook 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 off hook state, draws loop current from the C.O. thereby signaling that service is being requested.

Loss
Undesired (typically) 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.

Multicast
In networking, a method of addressing Ethernet packets so that they are received by multiple network endpoints. Primarily used as a method of bandwidth conservation.

Multimodal Emergency Mass Notification
An emergency alerting system capable of disseminating information in many modes like voice, text, social media, email, etc.

Night Ring (loud Ringing)
A feature which provide either by a telephone system, a page control or a peripheral common audible ringing device. Night ringing provides a signal, usually over the paging system, to indicate that a telephone line is in a ringing state.

Noise
Any undesired audio signal.

Non-Polarized
Not sensitive to the applied signal’s polarity.

NTP Server (Network Time Protocol Server)
A server, local or remote, that is defined to provide time to other network endpoints and servers, NTP servers provide a single enterprise-wide time standard for networked equipment.

Off-Hook
The condition that indicates the active state of a customer telephone circuit. This refers to the early days of telephony in which the telephone receive was removed from an actual hook/switch in order to place a call.

Off Premise Extension (OPX)
A phone extension located in a different building from common equipment.

One-Way Paging
Public address announcement without the benefit of hearing response from the paged area.

On-Hook
The state in which a telephone inactive. This refers to the early days of telephony in which the telephone receive was returned to an actual hook/switch at the conclusion of the call.

Open Loop Disconnect
See Calling Party Control

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.

Line Pool
See Trunk Group

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.

Paging System
See Public Address System

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 (typically speakers or horns) 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”.

Power Over Ethernet (PoE)
A method of powering network endpoints through the same cable used to provide network traffic. PoE eliminates the need for separate power cabling and simplifies system installations.

Potentiometer
A variable resistor. A movable sliding contact is used to vary the potentiometer’s resistance.

Public Address System
A voice amplification system used to provide audible information throughout a facility or enterprise.

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. Relay coils are rated in acceptable levels of activation voltage and current. Relay contacts are rated in the maximum voltage and current that they can switch. Often, low rated relays are used to actuate higher powered relays (a.k.a. slave relays) in order to control power intensive loads. Relay contacts that are open in an idle state (relay coil not energized) are referred to as Normally Open (N.O.). Relay contacts that are connected (shorted) in an idle state (relay coil not energized) are referred to as Normally Closed (N.C.).

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. Also the name of the one conductor of a telephone wire pair, designated by R. Also, One side of a line level audio pair.

Ring Cadence
The pattern of ringing a telephone terminal.

Ring Voltage
Voltage that is applied to a POTS telephone or telephone system in order to signal an incoming telephone call.

Ring back 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.

RSS Feed
Really Simple Syndication Format (RSS Feed) is an XML language used for web feeds.

Scalability
The ability for a system to increase or decrease in proportion to a facility’s needs.

Sensitivity
The level of audio signal into an amplifier required to achieve rated amplifier output.

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 to discourage the talker from speaking too loudly or too softly.

SIP (Session Initiation Protocol)
In IP telephony Session Initiation Protocol (SIP) is a communications protocol for signaling and controlling communication sessions. SIP telephones, Valcom IP speakers and many Valcom IP gateways may be used with IP telephone systems that support SIP.

Sound Reinforcement
Amplification of a line of site speaker’s voice such as used in auditoriums, classrooms and lectures halls.

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 hands free talkback systems (prevents eavesdropping).

Station (Intercom)
A talkback speaker and call button combination allowing users to request assistance from the speaker location.

Station Level Access
Accessing paging equipment 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 level access requires appropriate disconnect signaling to indicate that the origination telephone has returned to an idle (on-hook) state.

Station Port
An output on a telephone system where a POTS telephone terminal is connected.

Strike plate
See Electric Strike plate.

Subscriber
A telephone service customer.

Supervision (speaker or system supervision)
An automatic method of monitoring a paging or emergency mass notification system and reporting potential faults. Notification may be via e-mail, audible or visual alert or both.

Switch
A generic term for a KSU or PBX. In networking, a device which connects endpoints to the network.

Talk Battery
DC voltage applied through a trunk used to power a POTS telephone.

Talkback
A type of paging system in which individuals in the paged area can respond through the paging speakers of horns. Talkback speakers are speakers designed to be used with talkback controllers and are typically 25 volt or 45 ohm. A talkback speaker and call button combination, allowing users to request assistance from the speaker location, is a common combination.

Telephone Terminal
Another term for telephone. Telephone terminals may be proprietary to a particular system or may be designed to work with many telephone systems.

Telephony
Products and services related to the telephone industry.

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. One side of a line level audio pair.

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. In analog paging systems, a line level audio pair.

Trunk
A transmission channel connecting two switching machines. In telephony a trunk is a POTS telephone line.

Trunk Group
Two or more trunk ports that serving the same special purpose for inbound or outbound calls.

Trunk Port
See C.O. Line Port.

Unicast
In networking, a method of addressing Ethernet packets so that they are received by one network endpoint.

UPS
Uninterruptible Power Supply. A system of providing system power should facility ac power fail.

UTP
Unshielded twisted pair cabling. Often referred to as CAT 3/5/6.

Valcom Power Unit (VPU)
One Valcom power unit is equal to and defined as, 50mA @ negative 24 volts dc. Valcom power units were devised in order to aid in the determination of total system power required when configuring a Valcom paging system. The use of negative voltage is a nod to the world of telephony which also uses negative voltage. Negative and positive voltages are equally effective and simply use different reference points. Valcom products are rarely polarity sensitive.

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.

VoIP (Voice Over IP)
A modern day approach to distributing audio via a data network. VoIP systems have many advantages over analog systems and provide long term cost saving and inherent supervision.

Voltage
A measure of the electrical force that causes current flow in a circuit.

VSP
Valcom System Practice. Term used for some Valcom installation manuals.

WAV File
Waveform Audio File is a Microsoft and IBM audio file format standard for storing an audio bit stream on PCs. WAV files are recorded in various bitrates and formats.

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.

Zone
A group of speakers, horns or LED signs combined (in hardware or software) to receive common announcements.