Pulse code modulation time division multiplex telephone system

• US 3,924,077 A
• Filed: 07/05/1973
• Issued: 12/02/1975
• Est. Priority Date: 07/05/1973
• Status: Expired due to Term

• Current Assignee: Thomas R. Blakeslee
• Original Assignee: Thomas R. Blakeslee
• Inventors: Blakeslee, Thomas R.
• Primary Examiner(s): Blakeslee, Ralph D.
• Assistant Examiner(s): Stewart, D. L.
• Application Number:
  US05/376,843
• Time in Patent Office: 880 Days
• Field of Search: 179/15AL,18CC,15BS,15BD,15BY,15A 343/176,178,179 178/2A,63F
• US Class Current: 370/433
• CPC Class Codes: H04J 3/1641 Hierarchical systems
• CPC Class Codes: H04M 9/025 Time division multiplex systems, e.g. loop systems

Abstract

A pulse code modulation telephone system which allows a plurality of subscribers telephone sets to be connected at various points along a single wire pair. Each telephone contains circuitry for sending and receiving pulse coded speech samples at the proper instant within the time multiplexed frame. As the time slot assignment of each telephone is not fixed, it is possible to have several times more telephones on the line than time slots. Time slots are assigned only as needed by active telephones.

Claims

1. A time division multiplex telephone system comprising:

terminal means for transmitting and receiving a plurality of telephonic signals from one end only of a single bidirectional wire pair in a repetitive time frame format having a plurality of sequential E time slots transmitted from said terminal means in one time interval and a corresponding plurality of M time slots received at said terminal means in a different time interval, each of saId telephonic signals occupying a pair of E and M time slots; and

a plurality of telephones connected across said wire pair in parallel to said terminal means, each of said telephones including logic circuitry means for conditioning said telephones to receive and transmit bidirectional telephonic signals in an assigned corresponding pair of E and M time slots, said terminal means including means for receiving M sample transmissions at times which are delayed by round trip delays existing between said terminal means and respective telephones.

2. Apparatus according to claim 1 wherein said circuitry includes independent means in the terminal and in each telephone for selecting the first available time slot in the frame number assigned to the telephone to be connected.

3. Apparatus according to claim 1 wherein said logic circuitry includes assignment means for selecting on demand a vacant M time slot and the corresponding E time slot as said assigned pair of time slots for an outgoing call.

4. Apparatus according to claim 3 wherein said plurality of telephones exceed in number said plurality of E or M time slots.

5. Apparatus according to claim 3 wherein said assignment means is additionally responsive to the receipt of an identification signal from said terminal means for selecting a vacant M time slot and the corresponding E time slot as said assigned pair of time slots for an incoming call.

6. Apparatus according to claim 5 wherein each of said frames includes an identification bit position and a plurality of frames comprise a multiframe and wherein the assignment means of each of said telephones is associated with and responsive to the presence of a signal in the identification bit position of a different frame of the multi-frame.

7. Apparatus according to claim 6 wherein the logic circuitry of each of said telephones includes a frame counter for counting the frame number of the present frame with respect to the multi-frame, and means responsive to said frame counter for enabling said assignment means during the frame associated with said telephone.

8. Apparatus according to claim 3 wherein the logic circuitry of each of said telephones includes storage means for storing the presently assigned E and M time slot number, time slot counter means for counting the number of the present time slot and means for enabling transmission in response to coincidence between said storage means and said time slot counter.

9. Apparatus according to claim 1 wherein each of said frames includes a plurality of guard bands between the M slots to accommodate propogation delay from the most remote to the nearest telephone.

10. A time division multiplex telephone system comprising:

a first plurality of telephones each adapted to transmit and receive bidirectional telephonic signals in a bidirectional time division multiplex format;

a second plurality of bidirectional transmission pairs, said second plurality being less in number than said first plurality for connecting at least two of said telephones in parallel;

multiplexer means for interleaving the signals from said bidirectional pairs into a unidirectional time division multiplex format adapted for transmission over two unidirectional transmission paths and for separating and coupling the two unidirectional signals onto said bidirectional pairs in said bidirectional format; and

a pair of unidirectional transmission pairs connected to said multiplexer means carrying said unidirectional format signals from and to said multiplexer, respectively.

11. Apparatus according to claim 10 wherein said unidirectional format comprise T1 format.

12. Apparatus according to claim 10 wherein said bidirectional format comprises a repetitive time frame format having a plurality of sequential E time slots for transmission of signals from said telephones to said multiplexer and a corresponding plurality of sequential M time slots for the transmission of signals froM said multiplexer to said telephones, each of said bidirectional signals occupying a corresponding pair of E and M time slots.

13. Apparatus according to claim 12 wherein each of said at least two telephones includes logic circuitry for conditioning said telephone to receive and transmit bidirectional telephonic signals in a variably assigned corresponding pair of E and M time slots.

14. Apparatus according to claim 13 wherein the number of telephones connected in parallel exceeds in number said plurality of E or M time slots.

15. Apparatus according to claim 13 wherein said logic circuitry includes assignment means for selecting on demand a vacant M time slot and the corresponding E time slot as said assigned pair of time slots for an outgoing call.

16. Apparatus according to claim 13 wherein said assignment means is additionally responsive to the receipt of an identification signal from said multiplexer means for selecting a vacant M time slot and the corresponding E time slot as said assigned pair of time slots for an incoming call.

17. Apparatus according to claim 16 wherein each of said frames includes an identification bit position and a plurality of frames comprise a multiframe and wherein the assignment means of each of said telephones is associated with and responsive to the presence of a signal in the identification bit position of a different frame of the multiframe.

18. Apparatus according to claim 13 wherein the logic circuitry of each of said telephones includes an oscillator synchronized to the repetitive frame format of said terminal means to maintain synchronism between all of said telephones and said terminal means.

19. Apparatus according to claim 10 wherein said telephonic signals are pulse code modulated and wherein said multiplex means byte interleaves the signals from said bidirectional pairs.

20. A time division multiplex telephone system comprising:

terminal means for transmitting and receiving a plurality of telephonic signals from one end only of a single bidirectional wire pair in a repetitive time frame format having a plurality of sequential E time slots transmitted from said terminal means in one time interval and a corresponding plurality of M time slots received at said terminal means in a different time interval, each of said telephonic signals occupying a pair of E and M time slots; and

a plurality of telephones connected across said wire pair in parallel to said terminal means, each of said telephones including logic circuitry means for conditioning said telephones to receive and transmit bidirectional telephonic signals in an assigned corresponding pair of E and M time slots, said terminal means including means for receiving M sample transmissions at times which are delayed by round trip delays existing between said terminal means and respective telephones, and logic circuitry means for variably assigning said pair of E and M time slots so that a vacant pair of said time slots is assigned to a particular telephone only when needed to complete a call.

21. Apparatus according to claim 20 wherein said circuitry includes independant means in the terminal and in each telephone for selecting the first available time slot in the frame number assigned to the telephone to be connected.

22. Apparatus according to claim 21 wherein said assignment means is additionally responsive to the receipt of an identification signal from said terminal means for selecting a vacant M time slot and the corresponding E time slot as said assigned pair of time slots for an incoming call.

23. Apparatus according to claim 22 wherein each of said frames includes an identification bit position and a plurality of frames comprise a multiframe and wherein the assignment means of each of said telephones is associated with and responsive to the presence of a signal in the identification bit position of a different frame of the multiframe.

24. Apparatus according to claim 20 wherein saId plurality of telephones exceed in number the plurality of time slots in a frame.