Common Channel Signalling and the SubscriberDuring recent years, the dramatic progress made in the field of telecommunications has paved the way for the introduction of new and improved services. It will be of vital importance for TA’s to be able to satisfy customer demands regarding such services. Whatever new services come, and regardless of their implementation, one thing is certain: they will require signaling resources which cannot possibly be provided by the conventional signaling systems in use today. With conventional signaling, a large number of pieces and many types of signaling equipment are required. With Common Channel Signalling (CCS), the signaling equipment is limited to relatively few signaling links. These links are used for the transfer of signalling messages between SPC exchanges. One link can be used for signalling many simultaneous transactions and hence is called a “common channel”. The signalling information is digitally coded and transmitted in the form of discrete messages; each message being a discrete block of binary coded data. Each message is logically associated with the transaction concerned (e.g. the set up of a call on a certain circuit) by means of a label (address). To summarize, CCS makes it possible to transfer signalling information directly from one digital exchange to another without setting up a speech- path. As mentioned above, this “direct signalling” is an important feature for the efficient realization of certain new subscriber services. Later, this feature may also be employed for ordinary calls to investigate the status (busy, disconnected, etc.) of a called subscriber line, by setting up a speech path through the network. One important new service which will require CCS is call diversion. This involves automatically diverting a call destined for a particular number (the B- number) to another number (the C- number).Today the use of this facility is limited by transmission restrictions; a call may not be routed via more than a certain number of transmission links in tandem. With CCS, by returning the C- number to the calling exchange, the call may be routed to a path that meets transmission requirements. This also gives a better utilization of network resources, as the number of occupied circuits for a diverted call is reduced. For a fully developed diversion service, facilities for also charging the B- subscriber should be available. The A- subscriber would then only be charged for the cost of a call from A to B, whereas the B- subscriber would pay the additional cost to C. In cases where a call is rerouted at exchange A, the charging during the call will be performed at A. CCS will be used to transfer charging information from A to B after the call is completed. CCS may be used also in connection with the activities of diversion. Exchange B asks exchange C whether or not diversion to the C- number in the enquire message is allowed and the C exchange makes a positive or negative response. Moreover, the functions above may be applied to other diversion services such as “diversion to operator”; “diversion on no reply”; “diversion on busy”; “call transfer” etc. Completion of “call to busy subscriber” is another service planned in a digital network. When, available, this will mean a new call will automatically be established at the moment a B- subscriber becomes idle. A rational implementation of this service requires that the call status of both the A- and B- subscribers can be monitored continuously. Changes in call status would then be signaled to the remote exchange, together with the identities (numbers) of both the A- and B- subscribers. The exploitation of CCS will be a gradual process, which proceeds in step with the evolution of the telecom network as a whole. The potential of CCS can be illustrated by examples from the USA, where it is already an established technique. Here CCS is used in conjunction with centralized data bases to provide various subscriber services. When a call is established, information is exchanged between a particular switching center and a data base which gives instructions as to the way a call should be handled. For example, this technique will be employed for improving the already widespread INWATS services. It will be possible to call certain subscribers (companies, authorities etc.) without being charged for more than a local call, regardless of the destination of the call. These subscribers may be assigned a unique number (800…), which is automatically routed to one of the companies` offices. By using CCS, companies may centralize customer enquiry services, booking services etc. without discouraging customers from calling.
Electronic Automatic Telephone Exchange KVANT
Vocabulary
27. urban- городской
Text
The electronic automatic exchange is intended for operation as the city, rural, office- production, reference- information, dispatcher’s and mobile stations, as well as automatic switching and rural- suburban assemblies. Wide application of the digital switching and distributed data processing principles make the automatic telephone exchange perspective for the inclusion in the communication networks. The organization principles of the automatic telephone exchange made it possible: - to greatly extend the range of the subscriber’s line loads (up to 0.8 erlang / subscriber’s lines); - to increase the capacity by a simple connection of auxiliary blocks, 60 subscriber’s lines each, without any reswitching of the automatic telephone exchange blocks and cable wiring. The internal connection interlocks are practically avoided due to the use of the full-access high- capacity switching units. The use of pulse- coded modulation allows the combination of the speech and data transmission in the limits of the automatic telephone exchange, which provides for the operation within the digital network of the integrated servicing. The software consists of functionally independent modules, which ensures its high reliability and capability of improvement, due to the replacement of the old modules and addition of the new ones.
The Automatic Telephone Exchange ensures: Main types of servicing: - communication within the automatic telephone exchange; - outgoing and incoming automatic communication over the State telephone network; - outgoing and incoming automatic intercity communication (without dialing one’s own number and with dialing the latter); - incoming intercity communication from hand- operated switchboards; - outgoing and incoming automatic communication over the departmental telephone network.
Auxiliary types of servicing: constant number, determination of the calling subscriber’s number, registering of the incoming calls, registering of the outcoming intercity talks, number dialing abbreviation, direct communication, emergency communication, return call, transmission of a call during the talk, informing incoming call, making inquiries during the talk, temporary readdressing, permanent readdressing, night- time servicing, temporary inhibit, temporary selective restriction of communication, reminding. Communication and servicing capabilities: - open numbering at the output to the departmental networks; - organization of a by- pass direction communication; - special types of communication designed for use in reference- information and dispatcher’s automatic telephone exchanges (the “Servis” services, ticket reserve); - provision for informing the subscribers in compliance with a preliminarily assigned list; - registration of the duration and cost of a talk; - delivery of speech messages with the use of an electronic automatic informer. The automatic telephone exchange operates with the counter stations and employs different types of signaling over the physical connecting lines and with the use of the multiplex equipment. This purpose is served by various types of the sets of the connecting lines which make it possible to connect the automatic telephone exchange to the networks over the two-, three- and four- wire lines or channels formed by the frequency division multiplex equipment. The automatic telephone exchange is connected to the pulse- code modulation equipment directly to a group route. It provides for the establishment of two- and four- wire build- up connections and of the connection with the automatic telephone exchanges of the same type without the use of the auxiliary equipment, over a common signaling channel. The software of the central control device and of the processors is stored in an energy- dependent memory, and the variable part of the data, on the flexible magnetic disc drives, which makes it possible in combination with the initial starting system to reduce the time between the energizing of the automatic telephone exchange and the beginning of its functioning up to one minute. The automatic telephone exchange provides for any valency of the number. The equipment operates without noise. It is naturally cooled under the stationary conditions.
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