Office LAN

X.25 dataline monitor A dataline monitor with the capability to monitor X.25 (Level 3) packet-switched datalines has been introduced by Codex . Called the Digilog DLM IV, the portable monitor offers test and

monitoring facilities for checking V.24 datalines at traffic speeds of up to 19 .2 kbit/s . Users can isolate faults on their present and future private lines, dial lines and packet-switched lines. In

Portable testing of V.24 datalines

High-speed fibre optic transmitter A range of fibre-optic transmitter/ receiver units that can operate at up to 100 Mbit/s has been announced by Systron-Donner . are Codelink devices The suitable for military applications and use in severe environments . The basic series comprises the Codelink-100, providing up to 100 Mbit/s and the Codelink-20A, for handling speeds of up to 20 Mbit/s, with intermediate versions available for customised specifications. The series offers a low bit-error rate (10-9 in Codelink-20A and 10 -15 in Codelink-100), low power requirements, high security and electromagnetic shields to reduce interference . Codelink-100's transmitter uses a semiconductor laser with integral thermoelectric cooler, to provide stable operation over a wide temperature range, and a PIN

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photodiode with a wide dynamic range is used in the receiver . As a result, there are few restrictions on the input data bit pattern . features include Additional optional Manchester code (for synchronous operation), built-in power supply filtering, TTL/ECL inputs and outputs, an EMI shield and a flexible optical pigtail. (Systron-Donner Ltd., St Marys Road, Sydenham Industrial Estate, Leamington Spa, Warwicks . CV31 0 1 QN, UK. Tel: 0926 35411)

Office LAN A local area network that uses a Winchester-disc-based mass storage unit and a'daisychain' coaxial cable to connect up to 64 users has been announced by NEC . System software includes bad-

the X.25 mode, the unit strips data and displays X .25 information at frame and packet levels in industryaccepted abbreviations on its screen . It then identifies send and receive sides of transmission in correct timing relationships, labelling them DTE and DCE . Other features include three counters and two timers which allow response-time analysing and error counting. They also permit the user to count the number of poles per terminal over an indefinite period . The monitor also offers a 1 024 character segmentable output bufferwith nonvolatile memory, permitting capture buffer to be dumped into output buffer to retransmit captured data. Memory size is 12 kbyte of full-duplex, halfduplex, send-only or receive-only characters, and 12 000 attribute bytes. Nine standard codes are offered, plus a further optional code. (Codex (UK) Ltd ., 114/116 Thornton Road, Thornton Heath, Surrey, CR4 6XB, UK. Tel: 01 689 2101, Tx : 946847) 0

track identification and substitution, disc head movement optimization, general polling to ensure even response times to each terminal and automatic error detection and correction . 160 Mbyte of Winchester disc storage is provided . PC-8000 terminals can be used either with full access to the centrally held files or independently, using their own floppy disc drives . An individual terminal can be taken out of the network without data corruption or affecting the performance of the network . The network is compatible with NEC's version of CP/M, and local storage of floppy discs is available . In addition to the system's selfchecking routines, the user's own operating environment may be secured . File lock is also provided and record lock is available with appropriate program calls . (NEC Telecommunications Europe Ltd., NEC House, 164-166 Drummond Street, London NW1 3HP, UK. Tel: 0 01 388 6100)

computer communications