NEC Infoset 408 System Manual

							System ManualC - 1
Glossary of Terms 

This glossary is provided to help you understand terms and abbreviations used
throughout this document.
Table C-1  Glossary of Terms
Term Definition
Central Office (CO)Telephone company facility where subscribers lines are joined to 
switching equipment for connecting other subscribers to each other, 
locally and long distance. Also called CO, as in See-Oh. Sometimes 
the term central office is the same as the overseas term public 
exchange. Sometimes, it means a wire center in which there might 
be several switching exchanges.  
CORefer to Central Office.
Dial Pulse (DP)A means of signaling consisting of regular momentary interruptions 
of a direct or alternating current at the sending end in which the 
number of interruptions corresponds to the value of the digit or 
character. In short, the old style of rotary dialing. Dial the number 
five and you will hear five clicks.   See also DTMF.  
Dual Tone Multifrequency (DTMF)Dual Tone Multi-Frequency. A fancy term describing push button or 
Touchtone dialing. (Touchtone is a not registered trademark of 
AT&T, though until 1984 it was.) In DTMF, when you touch a button 
on a push button pad, it makes a tone, actually a combination of two 
tones, one high frequency and one low frequency. Thus the name 
Dual Tone Multi Frequency.  In U.S. telephony, there are actually 
two types of tone signaling, one used on normal business or home 
push button/touchtone phones, and one used for signaling within the 
telephone network itself.  See also Dial Pulse.
DPRefer to Dial Pulse.
DTMFRefer to Dual Tone Multifrequency. 
						

							Issue 1AInfoSet 408
C - 2Glossary of Terms
Hybrid SystemThis  term is used to describe a system which has attributes of both 
Key Telephone Systems and PBXs. The distinguishing feature is 
that a hybrid key system can use normal single line phones in 
addition to the normal electronic key phones.  A single line phone 
behind a hybrid works very much like a single line phone behind a 
PBX. The second distinguishing feature of a hybrid is that it is non-
squared.  This means that not every trunk appears as a button on 
every phone in the system.  In a non-squared system, you can have 
more trunks than you have buttons on each telephone. Some 
telephones will have trunks that others do not have and vice versa. 
This allow you to have more trunks on your telephone system than 
you have buttons on your telephones. This means, for example, that 
four executives can each have private lines and access to four 
trunks on a six-button telephone.
ISDNIntegrated Services Digital Network. ISDN comes today in two basic 
flavors -- BRI, which is 144,000 bits per second and designed for the 
desktop, and PRI which is 1,544,000 bits per second and designed 
for telephone switches, computer telephony and voice processing 
systems. Neither ISDN BRI or ISDN PRI is a standard service, 
though there are several standard configurations. ISDN BRI is a 
wonderful service in your home or office because it can give you 
video conferencing, and ultrafaster data communications. 
Key Function (KF)Refer to Squared System
Key Service Unit (KSU)The Key Service Unit is the main cabinet containing all the 
equipment, switching and electronics necessary to run a key 
telephone system. 
KFRefer to Squared System
KSURefer to Key Service Unit.
LCDRefer to Liquid Crystal Display
Liquid Crystal Display (LCD)Liquid Crystal Display. An alphanumeric display using liquid crystal 
sealed between two pieces of glass. The display is divided into 
hundreds or thousands of individual dots, which are charged or not 
charged, reflecting or not reflecting external light to form characters, 
letters and numbers. LCD displays have certain advantages. They 
use little electricity and react reasonably quickly.
MFRefer to Hybrid System.
Multifunction System (MF)Refer to Hybrid System.
PBRPush Button Receiver.  Instead of rotary dialing, buttons are pushed 
to generate the tones needed to place a phone call. Also called 
Touchtone or DTMF.  Table C-1  Glossary of Terms
Te r m D e fi n it i on 
						

							InfoSet 408Issue 1A
System ManualC - 3
Rotary DialingRefer to Dial Pulse
PBXPrivate Branch eXchange. A private (i.e. you, as against the phone 
company owns it), branch (meaning it is a small phone company 
central office), exchange (a central office was originally called a 
public exchange, or simply an exchange). In other words, a PBX is a 
small version of the phone companys larger central switching office. 
A PBX is also called a Private Automatic Branch Exchange, though 
that has now become an obsolete term. In the very old days, you 
called the operator to make an external call, except in Europe. Then 
later someone made a phone system that you simply dialed nine (or 
another digit -- in Europe its often zero), got a second dial tone and 
dialed some more digits to dial out, locally or long distance. So, the 
early name of Private Branch Exchange (which needed an operator) 
became Private AUTOMATIC Branch Exchange (which didnt need 
an operator). Now, all PBXs are automatic. And now theyre all 
called PBXs, except overseas where they still have PBXs that are 
not automatic
Squared SystemA squared system is a system where each trunk line  appears as 
the same button on each phone. The major advanced of the squared 
system is that you can go to any telephone anywhere in the system 
and punch any button for any trunk line and know it to be the same 
button for the same trunk line. This makes telephone operation less 
confusing.  However, there is a limitation to this configuration, you 
can only have as many trunks on your key system as you have trunk 
buttons on your key telephones.   (See also, Hybrid System.)
SwitchA mechanical, electrical or electronic device which opens or closes 
circuits, completes or breaks an electrical path, or selects paths or 
circuits.  
Tenant ServiceSome businesses acquire a telephone system too large for their 
needs so they sell parts of the service to smaller offices in their own 
building or in the surrounding community. There are two ways to 
make money on tenant service -- renting telephone equipment or 
reselling long distance lines. Theres more money on re-selling long 
distance lines. 
Touchtone DialingRefer to Dual Tone Multifrequency.
Trunk LineA communication line between two switching systems. The term 
switching systems typically includes equipment in a central office 
(the telephone company) and PBXs. A tie trunk connects PBXs. 
Central office trunks connect a PBX to the switching system at the 
central office.   Table C-1  Glossary of Terms
Term Definition 
						

							



 

 
 
 
 
 
 	
		 	



 

 
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