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Personal computer LAN
Automatic calling from data station Automatic calling and answering facilities for data communications networks are available with the Type 4816 automatic data station from Thorn EMI Datatech. The autocalling/answer sequence allows data collection and distribution on PSTN/midnight line service, optional V.25 and 100 series autodialling capabilities and a facility for automatically 'retrying' unobtainable data connections. There is a keypad entry of two telephone numbers up to 24 digits each, and dialling initiation time, a remote control connection for autocall initiation and the use of one or two PSTN lines in primary or standby private circuit modes. The data station is designed for desk-top, stand-alone applications and incorporates a control panel with an alphanumeric keypad, LED display, function control switch, audio monitor on/off, volume control and circuit status displays. The Type 4826 card version is intended for high-density rackmounted applications, with up to five vertically mounted cards being housed in a rack, together with a common mains power supply. Each card front panel has six LED circuit status displays and a multiway socket for connection to a separate control panel assembly, if required, for programming and/or testing each card in turn. Optional features include the circuit 109 and
circuit 110 status displays and timed alarms. For V.25 autocalling, one PSTN prime or standby line is used, with each number to be called being stored in the data terminal equipment (DTE) or its ancilliaries. Non-V.25 autocalling control by the DTE normally uses 100 series V.24 circuits, and DTE signals can be asynchronous or synchronous. One facility allows the device to autocall without using a specialised DTE. The 200 series connector is not used and no dialling information or call control signals are required from the DTE. Autocalling is achieved through a sequence of events, using the keypad or, alternatively, is initiated by the closing of a pair of externally connected contacts. The equipment will abort a call if the sequences are not completed within a preset time. (Thorn
EMI Datatech Ltd., Spur Road, Feltham, Middx. TW14 OTD, UK. Tel: 01 890 1477) []
Data station provides autocalling/ answer
Personal computer LAN Zynar has announced the Plan 4000 network, designed to support the IBM Personal Computer, as well as the Apple II and Apple III. The system allows personal computers to be connected to the same network by means of a plug-in Network Interface Card. Up to 255 stations of any mix of IBMs and Apples are supported on each network segment, and stations can be
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an arbitrary mix of servers and workstations. It currently supports up to 548 Mbyte of disc storage on a single file server, and hard discs are offered in 60 and 137 Mbyte formatted capacities. The system also includes an industry standard digital tape back-up capability, built into the file server unit. This high-speed cartridge tape drive
offers a choice of 20 or 45 Mbyte tape capacities. In following the ISO seven layer model, Zynar has incorporated Arcnet technology at the physical data link layers, while Ethernet protocols are incorporated as the network and transport layers. The baseband network uses token passing protocols and transmits at a rate of 2.5 Mbit/s. The topology is arbitrary (without loops) and it allows a maximum distance of over 6.5 km between any two stations on the network.
(Zynar Ltd., 122/3 High Street, Uxbridge, Middx. UB8 1JT, UK. Tel: 0895 59831, Tx: 896607) []
Scrambling device for broadcast TV M/A-COM Linkabit have introduced a digital security product for the satellite distribution of television programming. The VideoCipher system consists of a scrambler at the distributor's facility and descramblets at the cable affiliates' locations, and is designed to prevent the unauthorized reception of satellite signals by scrambling both video and audio portions of the transmission. The equipment uses the Data Encryption Standard (DES) algorithm of the US National Bureau of Standards, and the scrambling technique is highly complex. Digital error detection and correction techniques are used to maintain a high-quality signal to the television set during periods of noisy reception from the satellite. The system incorporates addressing and control functions in a highspeed data control channel which can provide accurate reception in the presence of channel errors. This control channel supports 64 000 different tiers and provides address space for over I 000M subscribers.
(M/A-COM Linkabit Inc., 3033 Science Park Road, San Diego, CA 92121, USA. Tel: 6194572340, Twx: 910 337 1277) []
computer communications
circuit 110 status displays and timed alarms. For V.25 autocalling, one PSTN prime or standby line is used, with each number to be called being stored in the data terminal equipment (DTE) or its ancilliaries. Non-V.25 autocalling control by the DTE normally uses 100 series V.24 circuits, and DTE signals can be asynchronous or synchronous. One facility allows the device to autocall without using a specialised DTE. The 200 series connector is not used and no dialling information or call control signals are required from the DTE. Autocalling is achieved through a sequence of events, using the keypad or, alternatively, is initiated by the closing of a pair of externally connected contacts. The equipment will abort a call if the sequences are not completed within a preset time. (Thorn
EMI Datatech Ltd., Spur Road, Feltham, Middx. TW14 OTD, UK. Tel: 01 890 1477) []
Data station provides autocalling/ answer
Personal computer LAN Zynar has announced the Plan 4000 network, designed to support the IBM Personal Computer, as well as the Apple II and Apple III. The system allows personal computers to be connected to the same network by means of a plug-in Network Interface Card. Up to 255 stations of any mix of IBMs and Apples are supported on each network segment, and stations can be
102
an arbitrary mix of servers and workstations. It currently supports up to 548 Mbyte of disc storage on a single file server, and hard discs are offered in 60 and 137 Mbyte formatted capacities. The system also includes an industry standard digital tape back-up capability, built into the file server unit. This high-speed cartridge tape drive
offers a choice of 20 or 45 Mbyte tape capacities. In following the ISO seven layer model, Zynar has incorporated Arcnet technology at the physical data link layers, while Ethernet protocols are incorporated as the network and transport layers. The baseband network uses token passing protocols and transmits at a rate of 2.5 Mbit/s. The topology is arbitrary (without loops) and it allows a maximum distance of over 6.5 km between any two stations on the network.
(Zynar Ltd., 122/3 High Street, Uxbridge, Middx. UB8 1JT, UK. Tel: 0895 59831, Tx: 896607) []
Scrambling device for broadcast TV M/A-COM Linkabit have introduced a digital security product for the satellite distribution of television programming. The VideoCipher system consists of a scrambler at the distributor's facility and descramblets at the cable affiliates' locations, and is designed to prevent the unauthorized reception of satellite signals by scrambling both video and audio portions of the transmission. The equipment uses the Data Encryption Standard (DES) algorithm of the US National Bureau of Standards, and the scrambling technique is highly complex. Digital error detection and correction techniques are used to maintain a high-quality signal to the television set during periods of noisy reception from the satellite. The system incorporates addressing and control functions in a highspeed data control channel which can provide accurate reception in the presence of channel errors. This control channel supports 64 000 different tiers and provides address space for over I 000M subscribers.
(M/A-COM Linkabit Inc., 3033 Science Park Road, San Diego, CA 92121, USA. Tel: 6194572340, Twx: 910 337 1277) []
computer communications