BLF Busy Lamp Field indicators, or extension status indicators, provide information about the status of every extension on the telephone system. By looking at the BLF, you know whether an extension is busy or engaged. These are found on key systems and are not required for every user, only for those who are routing most of the calls or those who need to see the status of a number of extensions. Where a dedicated operator is required, special BLF consoles can be fitted to the side of the operator’s terminal to expand the number of indicators available.
BRAIF Basic Rate Access Interface. Interface card for access to basic rate ISDN.
BREAK IN The ability to dial directly into a local PBX, and then across a private network of PBX systems from an external exchange line.
BREAK OUT The ability to dial across a private network and to then access an exchange line at a suitable terminal PBX in order to enable the call to be charged at the “local rate”
BRI Basic Rate Interface. Access to the ISDN service at 144Kbps provided as two B data channels of 64Kbps and one D control channel of 16Kbps (2B+D).
BUSY HOUR The continuous 60-minute period during any measurable period when the calls handled by the system is at maximum.
