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Fmro-op range of local area nelwerk Systron-Donner Ltd. has introduced a fibre-optics data communications system which is compatible with the Ethernet...

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Fmro-op range of local area nelwerk Systron-Donner Ltd. has introduced a fibre-optics data communications system which is compatible with the Ethernet local area network. The company claims that the system, marketed under the name of Codenet, operates extremely efficiently over an area of more than ten times that covered by a coax cable serial bus Ethernet system. Switching from coax to Codenet fibre-optics is claimed to provide a number of benefits. Not only does the Codenet system ensure improvements in performance, data security, electromagnetic inference immunity, and low attentuation, but it is also technically superior in the three important areas of flux budget, bandwidth and collision detection, says Systron-Donner. As typical Ethernet systems are limited to 2.5 km between nodes, a circumferential coaxial cable system covers only 0.5 km 2 and incorporates four repeaters. A Codenet fibre-optic Ethernet system, however, can cover an area of 5 km 2 without a single repeater - and still maintain all stan-

dard Ethernet timing considerations. Larger areas can be covered by adjusting protocols to allow for timing changes. The size of a Codenet local area network is constrained only by the timing considerations of these protocols. Codenet has been developed by New York-based Codenoll Technology Corporation, which has an exclusive marketing agreement for the UK with Systron-Donner. The Codenet-2020 fibre-optic Ethernet transceiver is plug compatible with all Ethernet equipment. Data security, essential in many applications, but particularly for financial, government and military purposes, is assured. By using fibre-optics, it is virtually impossible to tap the data bus without being detected immediately. Problems such as ground loops, crosstalk and lighting are eliminated. As the Codenet Ethernet system is interconnected by glass fibres, no electrical signals of any kind are transmitted between equipment. It is claimed that Codenet can

Telex commmdcatoroperates at 300 bit/s Format Communications has introduced a compact telex communicator, the CTC, which is an eight-bit parallel microprocessor, with a cycle time of 1 ms. It incorporates 72 instructions, with an average instruction time of 3 ms. The system is aimed at the smaller one- or two-line user, and the company is confident that it will capture a big slice of the telex-replacement market. The system has three internal and 12 directly addressahle working registers. Designed and manufactured by Format, the central processor has proved reliable in service and has a meantime between failure rate over 25 000 hours. The system CTC uses 64 kbyte of static RAM, plus a 'bootstrap' loader, consistingof I k of ROM. Two telex lines are standard on the system with an option to add two

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more if required. The system also provides four lines as standard for connection to printers, teleprinters, word processors or computer systems. A further four lines, as well as extra disc storage space can be added if, for example, an internal 'electronic mail' network is required. The standard system incorpor++tes a floppy disc store of 250 k capacity; this can be used for messages, as well as a large library of address codes. By operating at 300 bit/s between terminals rather than the normal 50 baud teleprinter speeds, the system can be connected to the British Telecorn Datel Service, which uses the public telephone network. It can also be connected to leased lines in private telegraph networks. (Format Com-

munications Ltd, Longbridge Way, Cowley Mill Road, Uxoridge, Middlesex, UK. Tel: (0895) 30078)

detect data collisions accurately over much greater distances than a coaxial cable system. This is achieved through a combination of Codenoll's proprwtary collision detection technology, much greater bandwidth and lower attenuation of optical fibres. For the same reason, data can be transmitted between nodes over much greater distances. (5ystron-Donner Ltd, St Marys

Road, 5ydenham Industrial Estate, Leamington Spa, Warwickshire C V31 IQN. Tel: (0926) 35411)

Inmos get their 16x4-64 Inmos, the UK chip manufacturer, has launched a 16k x 4 version of the 64k dynamic RAM. A I00 ns access time (160 ns cycle) puts the IMS 262P in a strong position in world markets. The chip is aimed at applications m personal computers (to reduce chip count) and where a high memory bandwidth is needed, such as for high resolution graphics. The 2620 comes in three versions, with access times of 100 ns, 120 ns or 150 ns and worst case cycle times of 160 ns, 190 ns and 230 ns respectively. I nmos has carried over a feature on their previously announced 64k x I 2600. The refresh-assist is CAS before RAS. This means that certain functions can be carried out without external support. The chip is made using Inmos' double poly NMOS process. Maximum power dissipation is 495 mW (active) and 28 mW (standby). It is packaged in a plastic DIP with Jedec 18-pin standard pinout, making it compatible with its Texas Instruments rival 16k x 4. The Inmos device does not have page mode. The 100-piece pricing is $I 3.70, $10.40 and $8.80 for the 100 ns, 120 ns and 150 ns chips respectively. Delivery time is said by Inmos to be 2 - 8 weeks. An 8k x 8 RAM is scheduled for release later this year, says Inrnos.

(In,mos Ltd, Whitefriars, Lewins Mead, Bristol BSl 2NP, UK. Tel." (0272) 290861. Telex: 444 723)

mtcroprocessors and microsystems