ompany) One of several independent telephone panies created from the breakup of AT&T. RBS (Robbed Bit Signaling) A type of channel-associated signaling used in North America on T-1 trunks in which one of the bits of digital voice is stolen and replaced with the proper sig- naling bit. RC4 (Rivest Cipher 4) A streaming cipher technique. A stream cipher adds the output of a pseudorandom number generator bit by bit to the sequential bits of the digitized plain text. (random early detection) A queue management algorithm and a congestion avoid- ence algorithm that monitors the average queue size and drops packets based on statistical probabilities. redundancy (1) The portion of the total information contained in a message that can be eliminated without loss in essential information. (2) The provision of duplicate, backup equip- ment to immediately take over the function of equipment that fails. (3) In a database, the storage of the same data item or group of items in two or more files. redundancy check An automatic or a programmed check based on the systematic insertion of components or characters used especially for checking purposes. regenerative repeater (1) A repeater used in telegraph applications to retime and retrans- mit the received signal impulses and restore them to their original strength. These repeaters are speed and code sensitive and are intended for use with standard speeds and codes. (2) A repeater used in PCM or digital circuits that detects, retimes, and reconstructs the bits transmitted. (3) A LAN interconnect relay device that copies electrical signals from one LAN to another. Also called a regenerator. register The first unit in the assembly of common control equipment in an automatic exchange. The register receives address information in the form of dial pulses or DTMF signals and stores it for possible conversion or translation. reliability The measure of a network's availability. Reliability is often measured in terms of the number of nines; for example, five-nines reliability means that the 