Telephone terms and definitions
2500 (Set or Phone)
Usually refers to a basic single line phone.
A block of connectors where phone wires are
connected to. Usually a 25 pair amphenol cable goes from the KSU to the 66 Block.
Refers to the plug found on 25 pair cables used in
telephone wiring. Sometimes found in other sizes like 18 pair.
Short for analogous or "similar to". Refers to telephone transmission and/or
switching which is not digital. Analog transmission of sound or information uses
"waves" of electricity, converting sound waves to electrical waves.
The capability of a terminal, modem or a computer to answer a call and set up a data
connection without anyone being there.
A device or a feature of some voice mail units that answers a call and lets the caller
route their call to a specific extension or group.
Feature switches un-answered incoming calls to a back-up position after a pre-determined
interval of time. (If a call is not answered at station X, after a set time limit, the
call is transfered to Y).
Auto Call Distribution. A specialized phone system used for handling many incoming phones
which distributes the calls in a logical pattern. (If calls are coming in slowly they
won't always ring at the same location keeping one secretary busy while the others read
the morning paper).
Retains program if power is lost. Larger units can keep the phone system running for a few
hours without power.
Busy lamp field. Shows what other extensions are already using the phone.
Card, Printed Circuit Board (PCB).
The test phone used by telephone installers.
The electrical box that contains the boards. Usually called the Key Service Unit (KSU).
Feature which allows an incoming call to be sent elsewhere.
The PCB that plugs into the control unit or cabinet. CPU card, Station card, CO card,
CAT 3 Cable
Up to 25 Mhz communication.
CAT 5 Cable
Up to 100Mhz communication.
Service offered by the phone company. Provides single line service with many more
features. Typically, the user must sign a 3,5, or 7 year contract and can save up to 35%
on business phone lines. You need to dial 9 to get an outside line.
Central Office. Provides phone lines to your home or business, with a limited number of
phone coverage. (Your ordinary, basic phone line).
Connecting 3 or more people into one phone conversation whether inside or outside the
system. Different phone systems can handle a different quantity of simultaneous conference
Refers to handset cord ( the curly cord that goes from the phone to the handset), line
cord ( the flat cord between the wall jack and the phone). Line cords come in 2, 4, 6, and
8 conductor leads.
Central Processor Unit. Controls system functions. Also, referred to as the Central
Processor Board (CPB), Enhanced Processor Board (EPB) or ECPU. (The brains of a system).
Cathode Ray Tube. A terminal used for programming or in some instances, to view and answer
calls. (Your basic monitor).
Point of access to a computer that used trunk or lines for transmitting or receiving data.
A phone can have a data port which allows you to connect another phone related device such
as a fax or modem.
To return the system to its basic initial program.
The paper strip where you write the telephone number or extension. Also called
The tone that is heard when accessing an outside line. The same tone you hear when picking
up your home phone.
Direct Inward Dial. Dialing a number to reach a specific person or department. That call
would only ring at the specified phone.
In recording, the use of binary code to represent information. More accurate form of
transmitting information. Digital transmission of sound or information breaks down a
"sound wave" into tiny sections of (1's and 0's code). The code then needs to be
built back into a "wave" at the recieving end. Data is less susceptible to
interference because electrical "noise" does not build up the signal wave.
Direct Inward Station Access. A person can call into the system, from away, and access the
system to make intercom calls or call back out on another line.
Do Not Disturb. Most phone systems have this feature to stop incoming calls and intercoms.
Direct Station Selection. Access another station with one key press, and view who is
already on the phone. (see BLF). Usually a free standing phone unit. Some phones have DSS
Dual Tone Multi Frequency. Tones that are heard when dialing on an outside line or single
If you don't know it's because you are one. (The user who ends up using the items
purchased by a wholesaler or interconnect).
Electrical Programmable Read Only Memory. Software is stored in these chips, and they will
not loose there information with a power loss. Can be erased with ultra-violet light and
reprogrammed many times.
Electrical Erasable Programmable Read Only Memory. Same as above but can
be erased elecrically.
A unique number that identifies a phone. Extension numbers usually start with 10, 20, 100
,301, 3001. Sometimes referred to as an intercom number.
A way of drawing dial tone by grounding one lead on the CO card.
Talking on the phone without picking up the handset. You may have handsfree on intercom
but not on an outside line. A true speakerphone can communicate on an outside line without
lifting the handset.
Mechanical or electrical switch used to terminate a call. The handset usually depresses
the hookswitch when it is returned to the cradle.
The way inside callers communicate to other "inside" people using their phones.
The physical hook-up and diagnostic testing of a PBX switch, cabinet, or peripheral item
prior to a cutover and maintenance acceptance by the maintaining vendor. (Basically,plugging
all your phones into the KSU and programming it so all the telephones work properly).
A company that sells, installs and maintains telephone systems for end users. The larger
ones carry inventory and have a technical staff. What's an "end user"? if you
don't know it's because you are one. (The user who ends up using the items).
Telephone instrument. (multi line) Also known as "Voice terminal." (Your basic
business phone.) Don't try plugging one in at home, or a home phone inplace of a keyset.
They may look the same but they are completely different!
Key Service Unit. The main cabinet that holds the cards, or self-contained units. Most
multi-line phones plug into a KSU. The KSU controlls all the calls, which phones ring at
certain times, and everything else your phone system does.
Last Number Redial
Hit a button and the phone will redial the last number dialed.
Liquid crystal display, usually called a display phone. Can be added to some phones when
needed. Usually displays the time, extension number, and other usefull information.
Least Cost Routing. Feature that automatically chooses the lowest cost phone line to the
The lines that come into your building from the phone company. CO line or trunk line.
The cord that goes from the wall to the phone.
A way of drawing dial tone by completing an electrical loop on a CO port.
Main Distribution Frame. The panel where cables from the KSU are terminated. (A mess of
wires where the phone lines get attached to the KSU).
A light on the phone indicating there's a message for the user of the phone, either on a
voice mail or from another extension.
Equipment which converts digital signals to analog signal and vice-versa. (Hmmm.... and I
thought it was a device that communicates (usually over a phone line) with another device
(modem) to transfer data. Well... it converts digital 1's and 0's to a loud noise,
transmits it over the phone to another modem that converts the noise back into 1's and
A cord that has plastic clips on the ends. As opposed to one that is permanently hardwired
The outlet where a telephone is plugged into (RJ11).
Music On Hold
Background music heard when someone is put on hold. Can be pre-recorded or from radio
Off Hook Voice Announce. Allows someone to intercom you while you are on the phone with
someone else and use the speaker and microphone to communicate.
Off Premises Extension. Having a phone connected to your phone system that is usually not
in the same building.
Features that are activated on some systems. (Special stuff that you have to pay extra
for, even though the hardware and software are usually already there).
Upon dialing an appropriate code, any station may make a paging announcement through all
of the loudspeakers and other phones.
Private Branch Exchange. A switch used inside a private business as opposed to one serving
the general public. Various manufactures have different names for these such as: PABX,
CBX, EPABX, etc.. Most systems require dialing 9 to get an outside line.
Printed Circuit Boards or "Card" (The thing with all the colorfull little
doo-hickies and little black boxes that make it work).
A spot where you plug in a phone or a CO line. (A station card may have 4, 6, 8, 12 etc...
Punch Down Tool
The tool used to punch down phone wires onto a 66 Block.
Unplugging or momentarily turning off the power to a device. Some KSU's have a reset
switch. This sometimes needs to be done if the KSU has been bad or gotten confused and
doesn't work properly.
Ring Gen (90 VAC)
A device that produces 90-110 Volts AC. Used to ring a single line device.(Voice Mail,
Auto Attendant) ALL regular phone devices like fax machines, answering machine, home phone
etc.. need aprox. 100vAC at 30Hz to ring. Business phone systems use a low DC voltage
signal to tell the phone to ring.
The modular jack where phones or devices are plugged in (wall jack).
RJ11 = 4 conductor.
RJ12 = 6 conductor.
RJ45 = large 8 conductor.
Remember your grandparents phone where you had to
spin the wheel to get it to work. Well rotary dialing uses a sequence of pulses to
represent different numbers that are dialed. (If you were quick enough you can rapidly hit
the hookswitch 8 times to signify an 8 in a phone number).
A phone that can only access one line. Your home phone is a single line Phone.
A port on a card that will run single line phones.
The instructions the CPU uses to perform tasks. Stored on disks or chips (EPROMS).
Feature which allows the operator to converse with another party either inside the system
or outside without picking up the handset.
The ports or the telephone instruments. The different plugs you can connect a business
phone to on your KSU. Station 100, 101 etc...
The tones that are generated when dialing out or pressing a number on the dial pad (DTMF).
The phone line from the phone company. Can be ground start or loop start. (Don't let this
ground and loop stuff confuse you too much).
Most phone systems have the ability to transfer calls to another phone somewhere in the
building. Transferring calls usually puts the caller on exclusive hold and rings the phone
it was transferred to. Supervised transfer is when you are able to
announce the call to the station being transferred via the intercom function. A blind
transfer is when the call is transferred and simply rings at the new station.
When new features are introduced or problems resolved, the software version changes.
A device (usually a computer) that answers calls and allows the caller to leave a message,
gives the ability to send inter-office messages to groups, allows employees to retrieve
messages from both inside and outside the office and has an auto attendant feature.
Plastic can turn yellow over the years when exposed
to direct sunlight and/or florescent lighting. White plastic is effected the most, however
other colors can be effected as well.