Full duplex data set with half-duplex emulation

• US 4,599,719 A
• Filed: 06/18/1984
• Issued: 07/08/1986
• Est. Priority Date: 06/18/1984
• Status: Expired due to Term

• Current Assignee: AT&T Information Systems Inc. (AT&T, Inc.)
• Original Assignee: AT&T Information Systems Inc. (AT&T, Inc.)
• Inventors: Lawrence, Victor B., Day, Robert A. II, Zboray, Michael R., Breen, Robert N.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Rokoff, Kenneth I.
• Application Number:
  US06/621,517
• Time in Patent Office: 750 Days
• Field of Search: 370/24, 370/31, 370/32
• US Class Current: 370/296
• CPC Class Codes: H04L 5/16 Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission

Abstract

Half-duplex switched carrier operation is emulated in a full-duplex voiceband data transmission system by utilizing predetermined signal indications in each channel to signal the initiation and termination of user data in that channel and thus to control the Receive Line Signal lead extending to the terminals at respective ends of the transmission channel. The signal indication which signals the initiation of transmission is illustratively two scrambled spaces inserted into an idle-state sequence of continuous scrambled marks. The signal indication which signals the termination of transmission is illustratively a stream of 65 unscrambled marks.

Claims

1. A full-duplex data set adapted for use in conjunction with an associated first half-duplex data terminal, said data set being adapted to communicate to a second data set over an outgoing communication channel and to receive communications from said second full-duplex data set from an incoming communication channel, said second data set being adapted for use in conjunction with an associated second half-duplex data terminal, each of said terminals having a request-to-send lead which is activated by said each terminal when data is desired to be passed from said each terminal to the associated data set, and at least said first terminal further having a receive line signal lead and being adapted to activate its request-to-send lead only if its receive line signal lead is deactivated, said data set comprising

means for receiving near-end data from said first terminal,

means for modulating said near-end data signal onto a first continuous carrier signal and for applying the resulting modulated signal to said outgoing channel,

means for receiving from said incoming channel a second continuous carrier signal modulated with far-end data and for recovering said far-end data from said second carrier signal,

means for activating said receive line signal lead in response to a first predetermined signal indication in said received carrier signal and for deactivating said receive line signal lead in response to a second predetermined signal indication in said received carrier signal, said first signal indication being generated by said second data set in response to activation by said second terminal of its request-to-send lead and said second signal indication being generated by said second data set in response to deactivation by said second terminal of its request-to-send lead, and

means for applying to said first terminal the recovered far-end data that is intermediate said first and second signal indications.

2. A continuous carrier data set adapted for use in conjunction with an associated half-duplex data terminal, said terminal having a request-to-send lead and a send data lead, said request-to-send lead being activated by said terminal when data is desired to be passed from said terminal to said data set on said send data lead and said data set having a clear-to-send lead adapted to be connected to said terminal and which said data set activates when it is ready to receive said data, said data set comprising

means for generating a continuous carrier signal modulated in accordance with a modulating signal and for applying the resulting modulated carrier signal to a transmission channel, and

circuit means for generating sequentially as said modulating signal (a) a first predetermined signal indication generated in response to, and indicative of the activation of, said request-to-send lead, said circuit means being adapted to activate said clear-to-send lead at the end of said first predetermined signal, (b) the data appearing on said send data lead subsequent to the activation of said clear-to-send lead and prior to a deactivation of said request-to-send lead, said circuit means being further adapted to deactivate said clear-to-send signal in response to said deactivation of said request-to-send lead, and (c) a second predetermined signal indication indicative of said deactivation of said request-to-send lead.