Glossary

Numbers & Symbols

800 Service

A communication services where the receiving party pays for incoming calls. 800 services is often called Toll Free In the Americas and Freephone in Europe and the dialing digits are 0800. In the United States, additional toll free numbers include 888, 877, and 866.

A & B Signaling

A process of transferring signaling information on a digital communication line that involves the stealing of bits from the digital transmission line (called the A & B bits). This is a type of in-band signaling as it steals some of the channel bandwidth for use as signaling messages. When it is used in T1 transmission line, 1 bit of user data from each of the 24 sub-channels in every sixth frame is stolen (discarded) and replaced with signaling control information. The use of A+B signaling reduces the T1 bandwidth from 1.544Mbps to 1.536 Mbps.