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

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Fig. 4 Magazine for 8 modem units, rear view Mechanical dimensions, mm Width Depth Height Small desk-top case 212 420/450 60 Large desk-top case 130 390 250 Magazine 483 358 222 Advantages of the modular structure - Reduced cost ol spare parts - Small space requirements - Uniform appearance - Easy fault location - Easy exchange of transmission rate board can also be added within this space. The functional unit is connected by means of one or two euroconnectors at the rear. The board width is in accordance with the IEC297-3 recommendation, whereas the length is determined by market requirements. If necessary, the functional units can be reduced to half the total height. Desk-top case There are two types of the desk-top case, with different numbers of functional units and different power units. The two types contain a back plane for power distribution and connection of, for example, data terminals and telephone lines. The modems can also be equipped with overvoltage protection. The small unit can be equipped with a 5W or 10 W power supply for 220/110 V or 240/120 V. A battery powered 48 V DC/ DC converter is also provided. The power supply for the large desk-top unit provides 18W and is powered by 220/110 V or 240/120 V. Magazine The magazine in the Series7 modular structure has a height of 5 modules, each of 44.45 mm. Power distribution and the connection of terminals and telephone lines is located on the back plane. This means that a functional unit can always be changed from the front without the terminal connector at the rear having to be adjusted. If overvoltage protection is required for the telephone lines the protectors are also located on the back plane, fig. 4. The power supply can be arranged in different ways. The modem AC power unit can be switched between 115 V and 220/240VAC. With DC supply, the modem is equipped with a power unit for 24 V or 48V. The magazine can also be connected directly to +5V, +12V and -12V DC. Cabinet The cabinet is 19" wide, 1 835 mm high and has a smoke-glass door. When used for desk-top modems the cabinet is equipped with shelves and two distribution frames at the rear, for the power supply and connection of telephone lines. When the cabinet is equipped with modems in magazines it needs no extra internal parts since the power and telephone lines are wired direct to the magazines. Products The Series7 modems can be divided into product families which have similar applications and characteristics. Modems for leased lines This product family comprises modems for telephone channels and baseband modems, fig. 5. A combination modem for 0-300bit/s duplex and 0-1200bit/s half-duplex transmission is available for telephone channels, as well as modems for 2400 and 4800bit/s. A four-channel multiplexer is also available as an option for the 9600 bit/s product. For physical circuits a baseband modem is provided which can be switched from 600 to 19 200 bit/s. All modems have built-in functions for fault location on the data circuit. Faults are located by the transmission and reception of data patterns and loop settings on the local as well as the remote modem. These functions are accessible from the modem front to facilitate fault location. The loop settings may also be controlled via the terminal interface.
178 Fig. 5 Modems in Series 7 Modems for switched lines The modem for 4800bit/s is a combination modem intended for both leased and switched lines. Parameters, such as transmit level and receive level ranges, can be preset separately for the two applications. If a fault should occur on the leased line, the modem can easily be switched for operation over an alternative line through the public switched network. There is a switch on the modem front panel for this purpose. The duplex modem for 2 400 bit/s has an alternative rate of 1200 bit/s. It can transmit data in two directions simultaneously over a two-wire circuit. The modem is equipped with automatic calling and answer. This modem is described in greater detail below. Modem for 2 400 bit's duplex transmission The modem is designed in accordance with CCITT Recommendation V.22bis, which means that it can send and receive data simultaneously over a twowire circuit. This is particularly important on switched lines, where with 2 400 bit/s it has hitherto only been possible to transmit data in the half-duplex mode. Since the most common protocols are half-duplex the main advantage of a duplex modem will in practice be shorter turn-around times. The terminal and computer determine the turnaround time in this case. The duplex circuit is obtained by dividing the telephone channel into two frequency bands with a centre frequency of 1.2 kHz and 2.4 kHz respectively. When the circuit has been set up, the handshaking procedure, with which each data transmission starts, is arranged so that the calling modem sends data over the lower channel and the answering modem over the higher channel. The modem can interwork with modems for 1 200 bit/s in accordance with CCITT Recommendation V.22. In such cases the modem is automatically switched over to 1 200 bit/s by the handshaking procedure. Automatic calling and answer are two essential functions in a modem for switched lines. The modem meets the new CCITT Recommendation V.25bis, which permits a call to be set up from a terminal and controlled via the normal terminal interface. The control wires can be operated in a different way from normal data transmission in order to allow the wires for the transmit and receive data to transmit commands and telephone numbers between the terminal and the modem. t|! .
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 and 24: Fig. 8 Transmission characteristics
Page 25: Most computer cabinets are 19" wide
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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