per second (Hertz). 120 GLOSSARY Baseband. The frequency band occupied by information-bearing signals before they are combined with a carrier in the modulation process. Baud. A unit of signaling speed. The number of signal elements per second where all such elements are of equal length and represent one or more information bits. Bit. A contraction of the term binary digit. A bit can be either 0 or 1 and is the smallest possible unit of information making up a character or word in digital code. Blocking. A condition where connections cannot be made due to "all lines busy". Bridge. Equipment used to match circuits to each other ensuring minimum transmission impairment. Bridging is normally required on multipoint data channels where several local loops or channels are interconnected. Broadband. Refers to transmission facilities whose bandwidth (range of frequencies they will handle) is greater than that available on voice grade facilities. Also called wideband. Buffer. A temporary storage device for data which cannot be used or retransmitted immediately. Buffered network. A data communications system which employs buffers associated with each terminal device to maximize the effi- ciency of terminals and facilities. Buffered terminal. A terminal containing a memory that stores in- put from the keyboard temporarily, until a transmit key is depressed. Bus. An electrical data path that serves as a common connection for a related group of devices. Byte. A sequence of normally 8 bits, operated on as a unit. Carrier. A high-frequency radio signal which is modulated to carry information long distances through space or via cable. CCITT. (Comite Consultatif International Telegraphique et Tele- GLOSSARY 121 phonique). The International Telegraph and Telephone Consultative Committee-an international organization concerned with devising and proposing recommendations for international telecommunica- tions. Central office (CO). The location of telephone switching equip- ment where customers' lines are terminated and interconnected