 also referred to as an octet. mation is encoded in the form of fields of one or more bits. It is usually more efficient than character mode or byte oriented protocols. Bits per second. Basic measure of the transmission capability of a medium. High speed channels are specified in kbit/s, Mbit/s Cable vault. Refers to the point where external cables enter a and Tbit/s. central office building. Bit stuffing. Process used in transmission for adding additional Call barring. System which restricts calls to certain numbers. bits at the receiving end which are removed and discarded at Call detail recording. Facility within a PABX to allow all calls to the receiving end. Examples are bit stuffing used for synchroni- be logged, to enable, for example, costs to be charged out to sation in plesiochronous transmission, and the zero bits added individual departments. to a string of one characters to prevent the receive interpreting Call forwarding. Feature available on some switches for allowing it as a flag. a user to direct all his incoming calls to another number. Block. Usually refers to a continuous sequence of information, Call waiting indication. A message given to a subscriber, who is such a block of bytes or characters. on the telephone, that another call is waiting to be connected. Blocked calls cleared. It is a service technique in which unservice- Calling number indication. The facility for displaying to a tele- able requests stay in the system, but are not served. A portion phone user the number of the party that is calling him. of their service time is allowed to elapse before service begins. Capture effect. When two signals at the same frequency arrive at This feature is also known as lost calls held or LCH. a receiver the output corresponds to the stronger of the two and Blocking. Blocking is said to have occurred if a network, switch not a combination of the two, which would result in inter- or access equipment is unable to provide a user a service due to ference. unavailability of a transmission channel, oft