User`s manual

U.S. Robotics I-modem Command Reference

Glossary • Page G-9

call-control signaling

Messages carried over the telephone network that route, set up, and tear down calls. In

ISDN, call control signaling goes on over the D-channel

and is kept apart from the data

carried on the B-channels.

call indicate

A call originating tone deÞned by ITU-T recommendation V.8.

carrier

A continuous frequency capable of being either modulated or impressed with another

information-carrying signal. Carriers are generated and maintained by modems via the

trans-mission lines of the telephone companies.

CCITT

Formerly an international organization that deÞned standards for tele-graphic and tele-

phone equipment. It has been incorporated into its parent organization, International Tele-

communication Union (ITU). Telecommunication standards are now covered under