mendations Techniques. Part of CEPT.) transmission.) Time Slot Interchange. (Switching system technique Upper Sideband. which switches between circuits by separating the USITA US Independent Telephone Association. signals in time.) Universal Synchronous Receiver/Transmitter. (A Time-Space-Time (Digital switching method.) device, usually an integrated circuit, which converts Tracking, Telemetry & Command. (Satellite an- data for transmission over a synchronous channel.) tenna.) US Telephone Association. Telecommunications Technology Committee. USTSA US Telecommunication Suppliers Association. (Japanese.) Unshielded Twisted Pair. (Cable.) Telecommunication Terminal Equipment. Transistor Transistor Logic. (Integrated circuit logic family.) Transistor Transistor Logic Schottky. (Faster ver- Voice Activity Detection. (Technique used in trans- sion of TTL.) mission systems to improve bandwidth utilisation.) Teletypewriter. (Usually refers to the transmission Value Added Data Service. from a teletypewriter, which is asynchronous ASCII Value Added Network coded.) Value Added Network Services. Tributary Unit. (Part of SDH. Ref: CCITT G.709.) Value Added Service. (See also VANS.) Telecommunications Users' Association. (UK.) Value Added Service Provider. Telecommunications Users' Foundation. (UK.) Variable Bit Rate. Tributary Unit Group. (Part of SDH. Ref: CCITT Virtual Container. (Transmission mechanism used in G.709.) SDH, CCITT G.709. Its signals are never presented Television. outside the network.) 62/18 Glossary Voltage Controlled Oscillator. (Component used in Workstation Function. frequency generating systems.) Zurerein der Electronissches Industrie. Virtual Container Crossconnect. (Synchronous Zentrasamt fur Zulassungen im Fernmeldewessen. crossconnect at the VC level. Used within the CCITT SDH hierarchy.) Visual Display Unit. (Usually a computer screen.) Voice Frequency. (Signalling method using frequen- Glossary of terms cies within speech band. Also called in-band signall- ing. Also refers to the voice frequency 