Time compression multiplex digital transmission system

• US 4,467,473 A
• Filed: 07/30/1982
• Issued: 08/21/1984
• Est. Priority Date: 07/29/1982
• Status: Expired due to Term

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Arnon, Ephraim, Barlow, Christopher J., Chomik, Michael W.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Rokoff, Kenneth I.
• Application Number:
  US06/403,311
• Time in Patent Office: 753 Days
• Field of Search: 370/29, 370/100, 370/104, 370/109, 370/48
• US Class Current: 370/288
• CPC Class Codes: H04L 5/1492 with time compression, e.g. operating according to the ping-pong technique

Abstract

A digital transmission system in which bursts of digital signals are transmitted in opposite directions over a two wire telephone loop at fixed frame intervals. Each signal burst is bounded by initial and final synchronization bits at its beginning and ending respectively. Synchronization is established by determining coincidence of the final bit of one burst, the initial bit of the following burst, and two gating signals having an equivalent time interval therebetween.

Claims

1. In a digital transmission system comprising;

means for transmitting bursts of digital signals of fixed length and at fixed frame intervals, each burst including initial and final synchronization bits at the beginning and ending respectively, of each burst; and

means for receiving the bursts of digital signals, including clock recovery means for generating clock pulses synchronized to bits of the digital signals received from the transmitting means;

the improvement comprising in the receiving means;

means, responsive to the clock pulses, for generating first and second one bit period gating signals coincident with the anticipated reception of the initial and final synchronization bits respectively in each frame; and

means for generating a signal confirming frame synchronization, in response to the simultaneous occurrence of the second one bit period gating signal and the final synchronization bit of one frame, and the first one bit period gating signal and the initial synchronization bit of the following frame.

2. A digital transmission system as defined in claim 1 in which the confirming signal generating means includes counter means for generating the first and second one bit period gating signals separated from each other by the fixed burst length, and separated from the next following first and second one bit period gating signals by the fixed frame interval.

3. A digital transmission system having a central station and a remote station each including transmitting and receiving means as defined in claim 1 for alternately transmitting and receiving bursts of digital signals over a single transmission path;

and in which;

the central station transmitting means initiates transmission of each burst at the fixed frame interval;

the remote station transmitting means initiates transmission of each burst immediately after the remote station receives a burst from the central station transmitting means;

the central station receiving means includes an automatic line build out unit at the input thereto;

gating means for feeding the received signal back to the automatic line build out unit to control the gain thereof; and

means for disabling the gating means during transmission of each burst and for a preselected number of bit periods thereafter, so as to prevent perturbations resulting from the transmitted burst of digital signals on the single transmission path, controlling said unit.

4. In a digital transmission system comprising:

means for transmitting bursts of digital signals; and

means for receiving the bursts of digital signals;

the improvement comprising;

in the transmitting means each transmitted burst beginning with an initial synchronization bit and ending with a final synchronization bit separated by a first preselected number of signal bits, the final synchronization bit separated by an interval equal to that of a second preselected number of signal bits from the initial synchronization bit of the following frame;

and the receiving means also including;

means for determining the number of synchronization bit intervals between the final synchronization bit of one transmitted burst and the initial synchronization bit of the next succeeding transmitted burst;

means for determining coincidence between the number of synchronization bit intervals between said final and initial synchronization bits of the one and the next succeeding transmitted bursts;

means for confirming frame synchronization when said number of synchronization bit intervals is equal to that of said second predetermined number of signal bits.