en caused by over- Carrier. In telecommunications refers to a continuous signal loading or traffic congestion. Blocking is usually measured as which is modulated with a second signal carrying transmitted the ratio of unsuccessful attempts to use an equipment to the information. total number of attempts. Carrier. Within electronic component technology it refers to the Blue box. Refers to any equipment which is used to gain access to holes or electrons which cause conduction in semiconductor the network in order to place unauthorised calls, usually to devices. make calls without charge. Carrier to noise ratio. Measure of the noise within a transmission Bounce time. The period over which mechanical contacts, for channel. It is the ratio of the carrier signal level to the noise example those of switches and relays, will bounce before fi- signal level within a transmission channel. nally remaining closed. Caterfone decision. A decision by the FCC, in 1968, to allow Bridge. A device which is used for connecting two LANs together, telephone subscribers to connect their own equipment to the where no protocol conversion is needed. It operates at Layers 1 telephone network, provided it did not harm the network. and 2 of the OSI seven layer reference model. band. Band of frequencies, in the range 4GHz to 6GHz, which Bridged tap. A pair of wires connected to a main cable and nor- is used for satellite and microwave transmission. mally left open circuited. It may then be used at a later time to Cell. Usually refers to the area covered by a radio base station in connect to a new customer. cellular transmission, or the packet of information in packet Broadband. Usually refers to any communication channel which switched transmission. has the capability to carry services with bandwidth exceeding Central office. Refers to the location where a switching system for that for voice. Broadband services cover high speed data and a public network is located. video transmission. Broadband is often used synonymously Centre du transit. The 