Selection and Testing of Electronic Components for LM

More documents

Recommendations

Info

Fig. 8 Block diagram of the line terminating equipment inZAD8-2 Electronic switch Resonant circuit Pulse regenerating circuit Strapping field Transformer Line bullding-out network DC-DC converter Signal path Fig. 9 Alarm functions in the line terminating equipment Absence of pulses, send direction Remote power feeding fault Absence of pulses, receive direction High error rate, receive direction Strappable combinatory logic Transmission path Fig. 8 shows the block diagram for the line terminating equipment in system ZAD 8-2. In the send direction the bipolar signal is converted from unbalanced to balanced form in the send transformer of the transformer unit. In the receive direction the signal is regenerated in the terminal repeater, which is identical to a one-way dependent repeater. If the repeater section is short, LBO networks with an attenuation of 30 dB at 4.224 MHz are connected in. The description above also applies for ZAD 2-3. In this case no LBO network is required, but a 6 dB flat attenuator can be strapped in the send direction, for example to reduce the cable crosstalk. Leaving out the LBO network has made it possible to incorporate the alarm circuit in the transformer unit. Remote power feeding The dependent repeaters along the line are power fed in series over the phantom circuit from the remote power feeding unit in the line terminating equipment. The same type of unit is used in both ZAD 8-2 and ZAD 2-3. The power feeding takes place at a constant direct current of 48 mA and a voltage of up to ±106 V balanced to earth. The distance between power feeding stations varies from about 20 to 40 km in the case of 8 Mbit/s and from about 40 to 60 km for 2 Mbit/s, depending on the repeater spacing and the voltage drop in the cable. This distance can almost be doubled by using extended feeding via separate pairs or by series connection of power feeding units. In order to ensure personal safety it is possible, by strapping, to limit the maximum output voltage to approximately 10 V if a break should occur in the powerfeeding loop, for example a cable break. Alarm, automatic changeover The line terminating equipments in ZAD 8-2 and ZAD 2-3 have the same alarm functions, fig. 9. Plug-in U-links are used to set up the desired connections between primary and derived alarms. The alarm state of the system is indicated by light-emitting diodes, which can be seen through the front plate of the unit. The line terminating equipment can be provided with an auxiliary unit which, in the case of an alarm in the receive direction, provides automatic changeover to another, predetermined system that serves as a standby, fig. 10. The automatic changeover, which is tied to single-cable working, is particularly attractive if the standby system goes via another cable or a radio relay link.
Fig. 10 Automatic changeover between two systems that operate as the working and standby system respectively. The changeover is initiated by the absence of a signal in the receive direction or too high an error rate on the received signal Line terminating equipment, system 1 Two-way dependent repeater Control logic Fig. 11 Line terminating shelves for ZAD 8-2 (top) and ZAD 2-3. The top shelf is equipped with two 8 Mbit/s line terminating equipments, the bottom shelf with four 2 Mbit/s line terminating equip- Mechanical construction The line terminating equipments are placed in M5 single shelves", fig. 11. A shelf holds four systems in ZAD 2-3 and two systems in ZAD 8-2. The same type of shelf is used for both single and two-cable operation and for different power feeding alternatives. In the 8 Mbit/s system, with its stringent demands as regards crosstalk between different parts, a one-way dependent repeater is used as the terminal repeater, which has been made possible by adapting the shelf. The interface connections are assembled at the left end of the shelf. Eight easily accessible coaxial contacts, the D interface, are mounted on the inside and outside of the left side member. The first contact position at the left end of the shelf is reserved for the L interface. This is used for connecting the line terminating shelf to the fault location equipment in the bay and for connect ing in the system alarm. The interface cables are placed in the left bay side member. The station cable is brought in to the following contact positions in the shelf via connection units. As regards the bay construction reference should be made to the description of the 30 channel PCM terminal equipment 1 and the M5 construction practice 4 . The flexible bay design permits mixed equipping of 2 and 8 Mbit/s line equipments, PCM multiplex, digital multiplexors and signalling equipments. When the bay is equipped with only line equipment it holds, apart from fault location equipment, 64 line terminating equipments type ZAD 2 — 3 or 36 line terminating equipments type ZAD 8-2. The line equipment is fed direct from the station battery -24 to -60 V. The alarm circuits are fed from —12 V.
Page 1: ERICSSON REVIEW 3 1977 SELECTION AN
Page 4 and 5: Selection and Testing of Electronic
Page 6 and 7: Fig. 2 Curve tracer The special typ
Page 8 and 9: Fig. 6 Humidity test High air humid
Page 10 and 11: 100 Type of check Type of component
Page 12 and 13: Fig. 12 Computer-controlled test sy
Page 14 and 15: 104 Fig. 16 Comparison of fault tra
Page 16 and 17: Fig. 2 Cable groups with the conven
Page 18 and 19: 108 Fig. 9 Take-up stand lor connec
Page 20 and 21: Insulation: Solid polyethylene Cond
Page 22 and 23: New Telephone Set Arne Boeryd and G
Page 24 and 25: Digital Line Equipments for 8 Mbit/
Page 26 and 27: Fig. 5 ALBO network for automatic e
Page 30 and 31: Fig. 13 Small repeater housing of t
Page 32 and 33: 122 Fig. 16 Fault detector shelf an
Page 34 and 35: 124 References 1. Lindquist, S. and
Page 36 and 37: LARS G ERICSSON AKE PERSSON Telepho
Page 38 and 39: 128 Fig. 3 Standardization of progr
Page 40 and 41: 130 Fig. 6 The control room in an A
Page 42 and 43: Table 3 Number of component faults
Page 44 and 45: 134 ence this as congestion or a "s
Page 46 and 47: ABJ 101-the Modern Public Magneto S
Page 48 and 49: Fig. 3 Line unit for 10 magneto lin
Page 50 and 51: " The maximum number of lines that
Page 52: TELEFONAKTIEBOLAGET LM ERICSSON ISS

Selection and Testing of Electronic Components for LM

Create successful ePaper yourself

Delete template?

Save as template?