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  1. Technology
May 31, 1988


By CBR Staff Writer

AT&T Co has announced its latest Primary Rate Interface chip set, one of the first commercially available to offer integrated carrier rate transmission for Integrated Services Digital Networking standards in North America and Europe. The AT&T Microelectronics package is tailored for networking private branch exchanges, public telephone exchanges and mainframes. The line now consists of five compatible chips, including two that AT&T thinks are particularly innovative – the T7115 Synchronous Protocol Data Formatter or Spyder-T, with 32-channel capability on a single chip. And the T7280 16-Channel Adaptive Differential Pulse Code Modulation Transcoder, which can compress 64 Kilobits of voice information to 32 Kilobits, doubling transmission capacity through one chip. The entire chip set is designed to offer a vertically integrated solution for multiplexing voice and data over the same line in high-speed telecommunications transmission. In addition to the T7115 Spyder-T and the T7280 ADPCM, the set includes the LC1046 T-1 Line Interface (North American standards); the LC1135 CEPT Line Interface (European standards), and the T7229 Framer. The set is intended to provide designers with a uniform, consistent and flexible means for ISDN B and D channel control at primary rate speeds. The T7229 chip performs the framing and synchronisation necessary for ISDN Primary Rate Interface in both North American and European digital carrier systems. It performs on-line and off-line frame oriented functions in both receive and transmit directions. The T7115 Spyder-T provides a means to control individual time slots, or channels, on the Primary Rate Interface. It performs low level HDLC/SDLC protocol formatting functions to offload the host central processing unit, and an on-chip direct memory access controller is there to help assure rapid transfer of information with minimum intervention by a host CPU. The T7280 pulse code chip uses an algorithm to reduce the bandwidth needed for digitised speech and other voiceband data signals, so that by placing the transcoding function at a customer site, users can double the capacity of their leased transmission facilities. Applications for the T7280 include T-1 multiplexers, subscriber carrier systems, channel banks and voice messaging systems. The LC1046 Digital Signal Interface provides a line interface between the network cross-connect and terminal equipment circuits. It performs timing recovery, receives pulse regeneration, and transmits pulse shaping and equalisation functions. No details on price or availability were provided.

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