Field Trial of Optical Fibre Cable-TV System Optical Fibre System for ...

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Modems Series 7 Christer Erlandson Ericsson has developed a new generation of data modems designated Series 7. The modem units have a new interchangeable modular structure. Different desktop cases are available. Alternatively the modem can be installed in a magazine, which is to be mounted in a 19" cabinet. There are several different power supply alternatives. The modular structure simplifies the stocking of spares for the modems and also the operation and maintenance of the data circuits. The author explains why a special modular structure was chosen for Ericsson's new modems, describes briefly the construction and the units in Series 7 and concludes with a more detailed description of the modem for 2400bit/s duplex transmission. UDC 681.327.8.001.6 modems design engineering Ericsson has been developing and manufacturing modems for data transmission since the middle of the 1960s and has also participated actively in the international standardization work carried out by CCITT. Ericsson has concentrated on modems meeting the requirements of CCITT series V recommendations, and has therefore become one of the major suppliers to telecommunications administrations. Hitherto Ericsson's modems have been designed as single units, standing on tables or shelves, but the Series 7 modems can also be installed in magazines for rack mounting in standard cabinets. The main reasons for abandoning the standard Ericsson construction practice BYB used for the previous modem generation are that two modems with horizontal BYB printed board assemblies would not fit into the 19" cabinets used in most computer centres, and that CHRISTER ERLANDSON Ericsson Information Systems AB the circuit board area is too small to hold a complete modem. The Series 7 modems have been developed to meet the demands from telecommunications administrations as well as from large and medium size end users in all countries where Ericsson is active. The new modular structure was developed for data transmission products, often mounted in 19" cabinets, which is flexible and very useful also for other products with similar mechanical requirements. The modular structure Requirements Data modems are usually supplied as single units to be placed on a table. They have a mains lead and a telephone cord for connection to a wall socket. In computer centres equipped with many modems these are often installed in cabinets with doors. The modem is then placed on a shelf, the mains is connected to a power distribution panel and the telephone cord to a telephone socket panel. The long cables are left dangling at the rear of the cabinet. Fig. 1 The Series 7 products consist of functional units that can be mounted in different cases
Most computer cabinets are 19" wide and the height is divided into a number of standard modules. For efficient utilization of the cabinet the modems should have a width equal to the whole or half of the cabinet width, and a height equal to a number of standard modules. The size of the printed boards in the BYB structure does not meet these requirements and Ericsson has therefore developed the Series7 modular structure. Objective The objective is to obtain a flexible structure that facilitates both installation and operation of data communication equipment, fig. 1. The different parts of the modem, the modulator, demodulator, control circuits and line interface circuits are assembled into a functional unit, figs. 2-3. This unit can be installed in different cases as required. Special cases are available for the modems when they are to be placed on a table or mounted in a cabinet. There are two types of the desk-top cases, a small one that holds one, horizontal functional unit, and a larger one with room for three units placed upright. If many modems have to be accommodated in a small space, a magazine should be used. It holds eight upright units and is mounted in a 19" rack or cabinet. Advantages The uniform mechanical structure simplifies the stocking of spares. The same type of case is used for several different modems. The functional unit used for one type of modem is the same whether mounted in a desk-top case or in a magazine. The uniform appearance makes for an aesthetically attractive product family. The fact that all functional units can be mounted in magazines saves valuable space in computer centres. The prewiring of power supply and telephone lines also avoids a tangle of loose cables in the cabinets. The different modems have the same type of connection to the back plane and can therefore be mixed arbitrarily in the magazine. This means that the operator can very quickly exchange the type of modem when so required. All modems have operator controls on the front, for example for changing data rate and for fault location using a test pattern and different loop settings. Mechanical construction Printed board assembly The functional unit consists of a printed board assembly with an area of approx. 200x300 mm and a total height of 43 mm. When necessary, a daughter if^^^^^^^ ti^^^^. jg»^ i \yjk •^"^^^^H • 5f i&f^lZ-ZM* ^^^^^^^^/ tr '**^ ma^EZ ^^^^^^^^^^' ' .^^ i^B •'** "&*'•*}*' ! Ä:; T l £**WM w m !% 1 - ;*
Page 1 and 2: ERICSSON REVIEW 4 1985 Field Trial
Page 3 and 4: Trial of Optical Fibre Cable-TV Sys
Page 5 and 6: Head end (HC] 280 Mbit/s Farsta aut
Page 7 and 8: 158 Switching equipment Fig. 7 Futu
Page 9 and 10: 160 Fig. 10 The teleconference room
Page 11 and 12: GERHARD GOBL Public Telecommunicati
Page 13 and 14: Fig. 5, above left Two-channel A/D
Page 15 and 16: Digital input signals Digital outpu
Page 17 and 18: Power ZAV 280/4 has individual powe
Page 19 and 20: Wavelength Division Multiplexing fo
Page 21 and 22: 172 Subscriber side BP-890 Controll
Page 23: Fig. 8 Transmission characteristics
Page 27 and 28: 178 Fig. 5 Modems in Series 7 Modem
Page 29 and 30: Computer Aided Production of Plasti
Page 31 and 32: Fig. 4 Product geometry displayed o
Page 33 and 34: Rectifier for Mobile Telephone Syst
Page 35 and 36: I OR | OFU OS I CMUP HlsHi W±±±h
Page 37 and 38: 188 Fig. 6 The rectifier with the o
Page 39 and 40: Fig. 9 Rectifier BMJ A01 001 with t
Page 41 and 42: The Renewal of the London Undergrou
Page 43 and 44: 194 Rickmansworth, and the Loughton
Page 45 and 46: 196 Fig. 5 Optical fibre cable rout
Page 47 and 48: 198 In planning the optical fibre n
Page 49 and 50: Fig. 9 The digital telephone DIAVOX
Page 51 and 52: 202 Fig. 11 Transmission equipment
Page 53 and 54: 204 Fig. 2 Automatic testing of mul
Page 55 and 56: 206 Relative occurrence for F Fig.
Page 57 and 58: Fig. 5 Field testing of a 140 Mbit/
Page 59 and 60: 210 Fig. 7 The system down time as
Page 61 and 62: MTBF (years) Equipment 2-5 Transmul

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