AT&T DS1/DMi/ISDN-PRI manual Cross coupling, Unrestricted digital data, Q.931, GL-6GLOSSARY

GL-6GLOSSARY

clear-channel signaling

clear channel transmission

codepoint

codeset

combination tie trunk

common- channel interoffice signaling

common- channel signaling

Common- Control Switching Arrangement (CCSA)

CRC

cross coupling

CSU

cyclic redundancy check (CRC)

See 24th-channel signaling and common-channel signaling.

A channel that does not use robbed-bit signaling and does not have the ones- density requirement for user data. For System 75 and System 85 applications, clear channel transmission happens whenever a channel’s signaling bits are transmitted in a separate channel and whenever the facility is administered for B8ZS line coding. See also 24th-channel signaling, restricted channel, and

unrestricted digital data.

A numeric value for a specific field of an information element (IE) and used as part of a Q.931 message, thus allowing identification and processing of the IE. For example, in the network-specific facilities IE, the value 1 in the feature/service field means that the requested facility is a service. See also Q.930

and Q.931 .

A group of 133 information element (IE) identifiers. In the Integrated Services Digital Network (ISDN) message structure, there are eight possible codesets, numbered 0 through 7. Codeset 0 is the set of IEs defined by the CCITT. Codesets 1 through 4 are reserved for future standards. Codeset 5 is for national use. Codeset 6 is for IEs specific to the local serving network. Codeset 7 is for user-specific IEs. See also AT&T standardized facility element.

An end-to-end transmission facility consisting of both digital and analog facilities. Generally, combination tie-trunks are digital trunks that terminate on a channel bank.

Signaling in which signaling information for each of the 23 information channels is multiplexed into a separate "common" channel. For AT&T products, the 24th channel is used as the common channel. See also signaling system number 7.

Signaling in which one channel of 24 carries signaling for the other 23 channels, permitting channels to be used to nearly full capacity. Also called alternate voice/data signaling, clear-channel signaling, or out-of-band signaling. See also 24th-channel signaling and clear-channel signaling.

A private telecommunications network using dedicated trunks and a shared switching center for interconnecting company locations.

See cyclic redundancy check.

In a duplicated system, the process where the off-line system clock synchronizer (SCS) checks the signal integrity of the on-line SCS.

See network channel-terminating equipment.

A verification protocol that ensures transmitted data was received without transmission errors. Data are sent in blocks. CRC compares the block’s appearance before and after transmission. If the appearance does not match, that block of data is resent. Data will usually be resent 10 times before transmission is abandoned.