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26 Simplified description of the setting up of a connection A brief account is given here of how a transit connection is set up with signalling via a separate signal transfer point STP, figs. 6 and 10. The call attempt starts with a signal transfer unit STU-L being connected in and receiving digits. After three digits a FUR is selected under the control of TCP. The corresponding FIR in exchange B is called by means of conventional line signalling. The TCP in exchange A reads the FUR label. It transfers the first three digits and the speech channel label to CCP, which then generates the initial address message, IAM. This signal is sent via the signalling channel to STP, where it is analyzed and the label is translated. The signal is then sent to exchange B, where it is analyzed by TCP on the initiative of the called FIR, which has been connected to a signal translation unit STU-I. If the call turns out to be to exchange C, a FUR is selected, which calls the corresponding FIR in exchange C. In the normal way the TCP in exchange B transmits a signal to CCP, giving the speech channel label of the selected FUR. CCP then sends IAM to STP, where it is analyzed and the label is translated before being sent on to exchange C. In exchange C TCP decides that the call in question is a terminating one and waits for the remaining digits. When these have been received in exchange A and transferred from TCP to CCP, the latter generates a subsequent address message SAM and sends it to STP. The procedure is then the same as for the initial address message. Thus SAM is transmitted via STP-^B->STP-^C, with translation of the speech channel label in STP and B. When the remaining digits have been received in exchange C the switching stage is set up and the line state of the B subscriber is determined. If the line is free, TCP sends the appropriate signal to CCP, which then sends the free signal and speech channel label for the FIR in question in the return direction via C-* STP-^B^STP-^A. This free signal results in the speech circuit being through-connected at these three exchanges. Result The field trial has provided valuable experience of the CCS system and its adaption to the national network at the local exchange level. The trial has shown that control system ANA 30 is Fig. 11 Signal terminal
Fig. 12 The principle for common transmission equipment and Individual equipment tor each type ot communication with the CCITT signalling system No. 7 References 1. Meland, F. and Rishoj, E.: Crossbar Exchanges in Arhus become SPC Exchanges. Ericsson Rev. 54 (1977):2, pp. 86-89. 2. Hinwood, J. D. and Clark, D. W.: Field Trial of CCITT Signalling System using AKE13. Ericsson Rev. 49 (1972):4, pp. 124-138. 3. CCITT Orange Book, Vol. Vl.2. 4. Morlinger, R. and Viktorsson, O.: ARE 11 -System Description. Ericsson Rev. 54 (1977):2, pp. 67-76. 5. Hemre, A. and Hagard, G.: The Software and Its Handling in ARE System. Ericsson Rev. 54 (1977):2, pp. 77-85. 6. Andersson, B. et al.: ARE Systems in Modern Networks. Ericsson Rev. 54(1977):2, pp. 54-66. very suitable for adaption to CCS signalling and for STP functions. With direct signalling between two exchanges the analogue version of system No. 6 gives a signalling time that is of the same order of magnitude as MFC and d.c. code signalling. In the case of transit traffic the link-by-link principle is used for CCS, whereas the faster endto-end signalling is used for MFC and d.c. code signalling. Thus in this case the signalling time is longer for the CCS analogue version than the other two methods. This becomes more apparent when the connection is made via two transit points with signalling via STP. However, it is possible to start the setting up process earlier, whereby the wait for the ringing signal —the post dialling delay — is reduced to a satisfactory level. The field trial has not, however, provided sufficient basic data for reliable cost calculations, and thus it has not been possible to make economic comparisons between a CCS and a MFC network. Plans for the future Signalling system No. 6 is now being introduced on many international telephone circuits. The interest in CCS has grown also in other parts of the telecommunications field, which has meant that the fundamentals of the system are having to be reconsidered. Thus it can no longer be assumed that CCS must only be suitable for international circuits, where the cost of the signalling equipment is not decisive. Now it must also be suitable for the national network, where the cost aspect is of greater importance. Since PCM is now beginning to be an economic form of transmission even for long distances, it is possible to use a 64 kbit/s digital channel for CCS. This means that the signalling rate can be increased, and furthermore the analogue modem will not be required. Finally the introduction of the digital group selector is now imminent. As was made clear in a previous article in Ericsson Review 6 this can be done with advantage even in an existing ARE network. This development will lead to a changed network structure and also the introduction of concentrators around the new exchanges. Moreover measures will then be taken to prepare for an integration of different forms of communication, such as telephony, telex, data, gentex, and also network management, maintenance etc. Consequently CCITT is now in the process of preparing a new CCITT system, No. 7. It will contain a message transfer part that is common for all forms of communication, and which will constitute the actual common signalling channel. Individual parts, fig. 12, foreach communication form will then be connected to the ends of the common message transfer part. The specifications for this signalling system are expected to be completed around 1980. The main features are already known, however, and thus it is possible to plan how the system should be used in principle. It is even considered that it will be possible to use the transmission principles of system No. 7 between concentrators and the parent exchange.
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 and 26: 21 HENNING ANDERSEN VILLYK. PEDERSE
Page 27 and 28: 23 signalling was to be carried out
Page 29: 25 Fig. 10 Simplified block diagram
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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