Selection and Testing of Electronic Components for LM

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130 Fig. 6 The control room in an AKE 132 exchange with maintenance panel, magnetic tape units and other I/O devices International maintenance centre, IMC In an international exchange it is naturally particularly important that the maintenance of the exchange and lines can be carried out efficiently and that suitable aids are available. CCITT recommend that the supervision measurement and testing of international lines and the associated telephone exchange equipment should be carried out at an international maintenance centre, IMC, in the international exchange. IMC comprises the following parts: ISMC Maintenance centre for the international exchange ITMC Maintenance centre for the international lines ISCC Administrative centre for coordination of the maintenance of exchange and lines. ISCC does not require any special equipment and will therefore not be discussed here. ISMC ISMC has access to functions for — supervising the operation — testing devices and localizing faults — carrying out traffic recording In AKE 13 these functions are built into the system and are reached via typewriters. The ISMC activities are therefore usually carried out in the control room of the AKE exchange, fig. 6. The AKE system provides ISMC with some fifty operation and maintenance functions for the switching equipment Some of these are: — supervision of fuses and control circuits — supervision of traffic disturbances, congestion and blocking. An alarm and printout are obtained when a certain threshold value is exceeded. The system also contains functions for a more detailed study of each disturbance — automatic and semi-automatic supervision of the quality of connections and calls through observation of randomly selected connections — automatic checking that each line has at least one call every 24 hours — automatic signalling check on outgoing lines
Fig. 7 Test desk for ITMC The desk contains, among other things, — a level meter — a variable oscillator — a frequency meter — a psophometer The desk can be connected to the lines either automatically via the switching stages In response to a command from the typewriter, or manually, via the U-link racks In - tracing of the connection path through the exchange for a certain connection - recording of changes in the state of devices in a certain connection - circuit tester for code receivers and code senders. The testing is initiated by a command or automatically from the disturbance supervision — periodic testing of the speech paths through the switching network — blocking of lines, devices and links by means of commands — traffic recording and the collection of statistics on line routes, device groups and link routes. There is a wide range of measurement types available in addition to those recommended by CCITT. ITMC Extensive equipment is placed at the disposal of ITMC for the maintenance of international lines: Measuring equipment for making fully automatic transmission measurements in accordance with CCITT recommendations. The measuring equipment is of two types. One type is designated ATME (Automatic Transmission Measuring Equipment) and carries out level and noise measurements on international 131 lines in accordance with CCITT recommendation No. 2. The other type consists of automatic test equipments; CCITT 12 which uses CCITT measuring methods Nos. 1 and 2 for routine checks of the transmission quality on international lines with signalling in accordance with CCITT system No. 4, and STC (Simplified Transmission Check) for routine checks on international lines with signalling in accordance with signalling system R2. The measurements are controlled by a previously stored program that indicates when the measurements are to be made and on which lines. A test desk with instrument for making manual or semi-automatic transmission measurements, fig. 7. As can be seen from fig. 8, these desks can be connected both to the station side of the junction line relay sets, via the selector network, and to the line side, via U-link racks (jack racks that give access out towards the line or in towards the station). U-link racks for connecting lines to the test desk. (Certain telecommunications administrations, however, consider that the U-link racks can be omitted, since a junction line relay set in an SPC ex- WilH UiUdl/r IP ,1
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/
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Page 30 and 31: Fig. 13 Small repeater housing of t
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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 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
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Selection and Testing of Electronic Components for LM

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