Multiplex communications – Wide area network – Packet switching
Patent
1985-06-21
1987-05-12
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
H04Q 1104
Patent
active
046655158
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
This invention relates to a telephone system which is an entirely digital system including a central exchange to which a plurality of telephone sets are connected via lines for transferring digital information in time division between the sets. The system is particularly suitable for smaller installations, e.g. intercom systems.
BACKGROUND ART
Generally, systems utilized in the prior art are not completely digitized all the way to the connected telephone sets. Instead they are analog systems.
DISCLOSURE OF INVENTION
Even in relatively small systems in the prior art, a central group selector unit is used for establishing calls between different subscribers. Since the systems are furthermore not digitized out to the telephone sets, this results in problems whereby such systems are technically complicated and provide expensive solutions.
SUMMARY OF INVENTION
It is an object of the invention to provide an improved telephone system.
The telephone system in accordance with the invention solves above problems by a system enabling the establishment of connections without a central selector and by being digitized up to and including the telephone set.
The inventive telephone system is thus a digital system in which a plurality of extensions can each be connected via its own telephone set to an exchange. Information between the subscribers is transferred in time multiplex, which means that each of the subscribers, when establishing a connection in the exchange, is assigned an unoccupied time slot (channel) for transferring information. As mentioned, the system includes a digital exchange where speech is PCM-coded and decoded in the telephone set. Each set is connected to the exchange for example by a two-wire connection, through which, inter alia, PCM codes are transferred to and from the sets in a so-called burst signalling system, which means that the signals are transmitted in groups or bursts. In 4-wire communication, the need of burst signalling is eliminated. The telephone sets also obtain their current supply through said connection. In its simplest form the exchange consists of a rack with a plurality of printed circuit boards (PCB).
The basic boards in the exchange are a central processor board EXCP, a line board LIDI for connecting ten lines, for example, and a speech control board CCDX with a plurality of call options. The exchange may of course be equipped with several line boards and several control boards, as well as other types of boards. Each PCB contains a regional processor RP which communicates with the central processor board via a common serial control bus SB.
The technical advantages of the system are of course that the possibility is afforded of easily offering a high degree of excellent service, i.e. a large selection of services simultaneously as a simple system makes for large cost advantages compared with known systems.
BRIEF DESCRIPTION OF DRAWINGS
The system in accordance with the invention will be described below in detail with reference to the accompanying drawings, in which:
FIG. 1 is a block diagram of a system provided in accordance with the invention; and
FIG. 2 is a block diagram of a line circuit DEC included in the system of FIG. 1.
DETAILED DESCRIPTION
As apparent from FIG. 1, the central processor board EXCP includes a central processor CP (a microprocessor of the type 6809), a control unit SP (a microprocessor of the type 68120) and the memory units RAM type 6116 (data memory) and E2PROM type 2816 (program memory).
All the PCB's (line board LIDI and speech control board CCDX) are connected to the central processor board via the common serial control bus SB. As mentioned, the line boards each contain a regional processor RP (a microprocessor type 6801), to which is connected a line circuit DEC, to which can be connected two lines. Each line board may contain 5 such line circuits DEC, each with two line connection facilities. All the line circuits DEC are, on the exchange side, via a first input/output connected to the input/output of said mic
REFERENCES:
patent: 4069399 (1978-01-01), Barrett et al.
patent: 4287590 (1981-09-01), Boute et al.
patent: 4370743 (1983-01-01), Moran
patent: 4581733 (1986-04-01), Sarson et al.
Gilen Christer W.
Kjellander Gunnar L.
Olms Douglas W.
Telefonaktiebolaget LM Ericsson
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