Time division exchange system having functions of compressing and expanding information

• US 4,823,342 A
• Filed: 02/09/1987
• Issued: 04/18/1989
• Est. Priority Date: 02/07/1986
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Hirai, Koji, Morita, Takashi, Kusaba, Akira
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Marcelo, Melvin
• Application Number:
  US07/012,175
• Time in Patent Office: 799 Days
• Field of Search: 370/109, 370/79, 370/80, 370/81, 370/58, 370/110.1, 375/30
• US Class Current: 370/521
• CPC Class Codes: H04J 3/18 using frequency compression and subsequent expansion of the individual signals

Abstract

A time division exchange provided with a plurality of compression circuits for carrying out signal compression in accordance with a plurality of compression laws and a plurality of expansion circuits for carrying out signal expansion in accordance with a plurality of expansion laws is operated in the following manner. In a case where the exchange is used as an originating exchange, a compression circuit provided in the originating exchange for carrying out signal compression according to a desired compression law is selectively used at each time slot, and information on the desired compression law is sent out from the originating exchange. Further, in a case where the exchange is used as a destination exchange, an expansion law to be used on the receiving side is selected on the basis of the above information, and an expansion circuit provided in the destination exchange for carrying out signal expansion according to the selected expansion law is selectively used at each time slot.

Claims

1. A time division exchange system having a function of compressing information such as an input signal on the transmitting side and a function of expanding the information on the receiving side, comprising:

an originating office;

a destination office; and

a tandem switch connected between said originating office and said destination office to effect communication therebetween, said tandem switch including;

(a) at least one compression means for compressing information such as an input signal in a accordance with one of a plurality of compression laws;

(b) at least one expansion means for expanding information such as an input signal in accordance with one of a plurality of expansion laws; and

(c) switching means for applying the to-be-compressed information selectively to compression means which carries out signal compression according to a desired compression law, at each time slot, and for applying the to-be-expanded information selectively to expansion means which carries out signal expansion in accordance with an expansion law corresponding to the desired compression law, at each time slot;

(d) means for counting the frequency of each compression law and for sending compression career information to the destination office; and

(e) means for receiving compression career information from the originating office and for judging whether or not received compression career information meets a predetermined condition and for preventing further signal compression when the received compression career information fails to meet the predetermined condition.

2. A time division exchange system comprising:

a plurality of compression means for compressing a signal in accordance with one of a plurality of compression laws;

at least one multiplexer for combining a plurality of signals, which have been compressed by said plurality of compression means, into a first multiple signal;

a plurality of expansion means for expanding a signal in accordance with one of a plurality of expansion laws;

at least one separation means for separating said first multiple signal into a plurality of individual signals;

transmission means for combining a plurality of signals into a second multiple signal, for transmitting said second multiple signal, and for separating said transmitted second multiple signal into a plurality of signals;

a plurality of first subscribers;

a plurality of second subscribers;

first switching means for selecting one of said plurality of compression means and one of a plurality of multiplexers at each time slot on the basis of a signal from one of said first subscribers, and for connecting the one first subscriber and an input terminal of the selected compression means, an output terminal of the selected compression means and an input terminal of the selected multiplexer, and an output terminal of the selected multiplexer and one end of the transmission means, at each time slot; and

second switching means for selecting one of a plurality of separation means corresponding to the selected multiplexer and one of said plurality of expansion means corresponding to the selected compression means at each time slot, and for connecting the other end of the transmission means and an input terminal of the selected separation means, an output terminal of the selected separation means and an input terminal of the selected expansion means, and an output terminal of the selected expansion means and a predetermined one of the second subscribers, at each time slot.

3. A time division exchange system according to claim 2, wherein a signal path for sending a common channel signal is provided between said first switching means and said second switching means, and information on a compression law which has been used, is sent from said first switching means to said second switching means through said signal path.

4. A time division exchange system according to claim 2, wherein said transmission means includes at least one tandem switch provided between said first switching means and said second switching means, and wherein said tandem switch is provided with means for counting the frequency of each compression law and for sending compression career information to the second switching means and means for receiving compression career information from the first switching means and for judging whether or not received compression career information meets a predetermined condition, and for preventing further signal compression when the received compression career information fails to meet the predetermined condition.

5. A time division exchange system according to claim 3, wherein compression career information is sent through said signal path.

6. A time division exchange system according to claim 3, wherein multiplex transmission means for combining the common channel signal on said signal path and a signal on a link which serves as a speech path, into a second multiple signal, is provided on the first switching means side, and wherein delivery means for receiving said second multiple signal from said multiplex transmission means, and for dividing said second multiple signal into said common channel signal and said signal on said link, is provided on the second switching means side.

7. A time division exchange system according to claim 2, wherein said plurality of compression means include a circuit for compressing a signal of 64 Kbps to a signal of 16 Kbps and a circuit for compressing a signal of 64 Kbps to a signal of 32 Kbps, said plurality of expansion means include a circuit for expanding a signal of 16KBPS to a signal of 64 Kbps and a circuit for expanding a signal of 32 Kbps to a signal of 64 Kbps, said plurality of multiplexers include a circuit for combining four signals of 16 Kbps into a multiple signal of 64 Kbps and a circuit for combining two signals of 32 Kbps into a multiple signal of 62 Kbps, and said plurality of separation means include a circuit for separating a multiple signal of 64 Kbps into four signals of 16 Kbps and a circuit for separating a multiple signal of 64 Kbps into two signals of 32 Kbps.

8. A time division exchange system according to claim 2, wherein said first subscribers include a plurality of telephone subscribers and a plurality of facsimile subscribers, and said second subscribers include a plurality of telephone subscribers and a plurality of facsimile subscribers.