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DATA TERMINAL AUTOMATIC CONTROL CIRCUIT

  • US 3,745,251 A
  • Filed: 01/03/1972
  • Issued: 07/10/1973
  • Est. Priority Date: 01/03/1972
  • Status: Expired due to Term
First Claim
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1. A circuit for controlling the operation of a communication terminal connected to a transmission system having a ring signal connection and a data transmitting connection, said terminal including a modem means switchably connected to said data transmitting connection, the modem having a data output and a carrier presence indicating output, said circuit comprising:

  • a. an answer abort timing means;

    b. a long mark timing means;

    c. a carrier loss timing means;

    d. logic circuit means connected to the outputs of said answer abort timing means, said long mark timing means and said carrier loss timing means for enabling operation of said terminal including switching said modem into connection with said data transmitting connection for receiving data in response to a ring signal and for maintaining said terminal in an enabled condition at least until the expiration of said first time period and thereafter so long as said long mark timing means and said carrier loss timing means are both in their said respective first states;

    said logic circuit further comprises;

    e. an alarm condition monitoring means having an output for switching from a first to a second state whenever said terminal is incapable of functioning properly;

    f. a local off switch means for manually presenting automatic operation of said terminal, said local off switching means having an output for switching from a first to second state for preventing operation;

    g. '"'"''"'"''"'"''"'"'nor'"'"''"'"''"'"''"'"' gate means having inputs connected to the outputs of said monitoring means and said local off switch means and having an output for switching from a first state to a second state whenever neither said monitoring means nor said local off switch is in its second state; and

    h. '"'"''"'"''"'"''"'"'and'"'"''"'"''"'"''"'"' gate means having inputs connected to the output of said '"'"''"'"''"'"''"'"'nor'"'"''"'"''"'"''"'"' gate means and the output of said answer abort timing means and having an output for switching from a first state to a second state whenever said '"'"''"'"''"'"''"'"'NOR'"'"''"'"''"'"''"'"' gate is in its second state, the output of said '"'"''"'"''"'"''"'"'and'"'"''"'"''"'"''"'"' gate enabling the operation of said terminal when in its second state.

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