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Fig. 4 Signal flow (T) Includes 11 bits that state which signals were received correct and faulty respectively Fig. 5 Example of a star-shaped signalling network with two signal transfer points STP1 and STP2 ^—• Alternative speech routes between A and B ~— Speech paths for STP1 ^ - Speech paths for STP2 O Exchange Signal transfer point STP A Local exchange A B Local exchange B Ti Local transit exchange 1 T2 Local transit exchange 2 synchronization units (SYU), when there is no need of real signal information. The bit stream is divided into signal units (SU) consisting of 28 bits, of which the last eight are check bits, fig. 4. With the aid of these the receiving signal terminal decides whether the received signal unit is correct or faulty. Twelve signal units form a block, with the twelfth unit consisting of an acknowledgement unit (ACU). The information from the check bits is transferred to ACU, where a decision is made as to which signal elements, if any, are to be returned because of faulty transmission. The previously mentioned synchronization unit (SYU) contains a determined bit pattern. Apart from its use as a filler to make up a continuous bit stream, SYU is used the first time the data link is started up. Only synchronization and acknowledgement signals are then sent until the signal terminals at both ends are synchronized at bit, signalling unit and block level. Digital version In the digital (PCM) version of signalling system No. 6 the following bit rates are used: - bit rates of 4 and 56 kbit/s for 30/32- channel PCM. This is the European standard and the signal bit stream is transmitted in a special time slot (No. 16) - a bit rate of 4 kbit/s for 24-channel PCM systems, which are widely used in the USA and Japan. Some facts concerning the field trial The following basic facts are given in order to make it easier to understand how the field trial model in its entirety functions. A SPC exchange of type ARE 11 always contains a control system ANA 30. When an ARF 10 exchange is modernised by the inclusion of ANA 30 it also becomes a SPC exchange, and its type designation is changed to ARE 11. The normal version of ARE 11 with ANA 30 and the associated software have been described in two articles in Ericsson Review 4-5 . Special processor functions are added for common channel signalling The normal version of ARE 11 contains two types of processors, namely traffic control processors TCP and operation and maintenance processors OMP. Signalling system No. 6 requires the addition of a common channel signalling processor CCP in the terminal exchange and a signal transfer point processor SPP for STP functions. All processor types consist of the same hardware. Thus if there is unused capacity in a TCP it can be provided with the required software and also used as CCP. Star-shaped signalling network In spite of the mesh-shape of the speech network in the Arhus area, the field trials were optimized for a star-shaped signalling network with two signal transfer points, STP1 and STP2, in accordance with the example in fig. 5. Each STP is normally situated in or near a telephone exchange, which does not need to be included in the speech connection but which transfers the CCS signals. Each exchange must then have at least one signalling channel to each STP, and the signalling traffic is usually divided equally between these channels (load sharing). This saves time since the queuing time is reduced, and also provides greater reliability because of the duplication. If a fault occurs in one channel, the signalling in question is transferred to the other channel. The maximum number of speech channels There is an upper limit to how many speech channels a signalling channel can serve, since it can only transmit a limited number of signals per unit of time. This limit is dependent on, for example, the average seizure time of the speech channel, and thus it varies in different applications. In the Mundelstrup trial, where the signalling channel could only transmit register signals, a signalling channel served approximately 1960 speech circuits, which would be reduced to 980 if the line signals were also included. Different signalling possibilities The analogue version of the signalling svstem was used for the field trial, but
23 signalling was to be carried out over the speech wires in accordance with the existing principles. The speech transmission paths were thereby automatically checked, and hence the continuity check of the speech paths recommended by CCITT could be omitted in the field trial. Fig. 6 Schematic picture of the Mundelstrup field trial equipment with a signal transfer point STP and signalling conditions that are typical for Arhus local exchange area Speech circuit A - B - C Signalling circuit A- B and the designation forcertain signals sent via it Signalling circuit B — C and the designation tor certain signals sent via it Fig. 7 Block diagram for the field trial equipment in Mundelstrup with common channel signalling CCP SPP GV-KME DC-I Common channel signalling processor Signal transfer processor Code receiver Interlace equipment Equipment that has been added tor the — field trial Equipment that has been changed for the field trial the software was also prepared for the digital version with a transmission speed of 4 kbit/s. Facilities were also provided for conversion between common channel and d.c. code signalling, as well as for connecting via two transit exchanges. As has been mentioned above, for this project it was decided that the line Traffic cases The field trial equipment consisted of a signalling link, with both ends connected to a processor in ANA 30 via a signal terminal. Another of the exchange processors could be connected in to and disconnected from the signalling link, and was thus able to function as a signal transfer point STP when required. In this way it was possible to set up connectionsthat represented signalling circuits within the whole of the Arhus local exchange area, including connection to transit exchange AKE 13. Fig. 6 shows how a local transit circuit from A to C is set up with signalling via STP.
Page 1: ERICSSON REVIEW 1 1978 OPERATIONAL
Page 5 and 6: ERICSSON REVIEW NUMBER 1 • 1978
Page 7 and 8: 3 STEN RIMBLEUS Stockholm Telecommu
Page 9 and 10: Fig. 4 (left) The operation and mai
Page 11 and 12: Types of faults, measures and subsc
Page 13 and 14: 9 ABDULLAH AL-SABEJ Chief Engineer
Page 15 and 16: Stored Program Controlled PABX, ASB
Page 17 and 18: 13 When the receiver is lifted the
Page 19 and 20: 15 five such matrices permit connec
Page 21 and 22: 17 Fig. 8 Printed board assembly fo
Page 23 and 24: Technical data Capacity Number of e
Page 25: 21 HENNING ANDERSEN VILLYK. PEDERSE
Page 29 and 30: 25 Fig. 10 Simplified block diagram
Page 31 and 32: Fig. 12 The principle for common tr
Page 33 and 34: PER-ALRIK HALLBERG THORWALD LUNDMAR
Page 35 and 36: 31 Fig. 9 Regulation range for the
Page 37 and 38: Fig. 12 Power feeding of the line r
Page 39 and 40: 35 oscillators also cease operating
Page 41 and 42: Technical data Electrical data Cabl
Page 43 and 44: 39 CHRISTOPHER LORENZ Financial Tim
Page 45 and 46: The Ericsson Group With associated

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