e. switched line A temporary connection between computers or devices that is established by dialing. switching Establishing a transmission path from a particular inlet to a particular outlet of a group of such inlets and outlets. switching center A location that terminates multiple circuits and can interconnect circuits or transfer traffic between circuits. Glossary switching system switching system A device that connects two transmission lines together. switchook A switch on a telephone set that is associated with the structure supporting the receiver or handset and is often used to signal the switching equipment or an attendant during a call. switchover A switch to an alternative component that happens when a failure occurs in the equipment. symmetric encryption Encryption in which the sender and the receiver use the same key or machine setup. synchronization The process of adjusting a receiving terminal's clock to match the clock of the transmitting terminal. synchronous (1) Having a constant time interval between successive bits, characters, or events. Synchronous transmission uses no extra information (such as the start and stop bits in asynchronous transmission) to identify the beginning and end of characters and thus is faster and more efficient than asynchronous transmission. The timing is achieved by transmitting sync characters prior to data. Usually, synchronization can be achieved in two- or three-character times. (2) Occurring with a regular or predictable time relationship. In data transmission, the time of occurrence of each signal representing a bit is related to a fixed time frame. synchronous communications High-speed transmission of contiguous groups of charac- ters in which the stream of monitored and read bits uses a clock rate to transfer the characters over a communication line. synchronous network A network in which all the communications links are synchronized to a common clock. Synchronous TDM (Synchronous Time Division Multiplexing) A method of TDM in which time slots on a shared transm