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Coding device selectively connected to a transmission line

  • US 4,807,250 A
  • Filed: 10/06/1986
  • Issued: 02/21/1989
  • Est. Priority Date: 10/04/1985
  • Status: Expired due to Fees
First Claim
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1. A coding device for coding for coding an input signal into a coded signal which is transmitted through a connection control circuit to a transmission line while said coding device is connected to said transmission line through said connection control circuit, said coding device comprising subtracting means for subtracting a local signal from said input signal to produce a difference signal, coding means for coding said difference signal into said coded signal, and local decoding means for locally decoding an internal code signal related to said coded signal into said local decoded signal, said coding device being selectively connected to said transmission line under control of said connection control circuit, wherein the improvement comprises:

  • code producing means for producing a predetermined code;

    selecting means, coupled to said connection control circuit and responsive to a control signal provided by said connection control circuit, for selecting said coded signal as a selected code signal when said control signal indicates connection of said transmission line to said coding device, and said predetermined code as said selected code signal when said control signal indicates disconnection of said transmission line from said coding device; and

    means for supplying said selected code signal to said local decoding means as said internal code signal.

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