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

• Current Assignee: Richard D. Fretwell
• Original Assignee: Richard D. Fretwell
• Inventors: Fretwell, Richard D.
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): D'Amico, Thomas
• Application Number:
  US05/214,628
• Time in Patent Office: 554 Days
• Field of Search: 179/2DP,2R,3,4 340/152,147R,208 178/66
• US Class Current: 375/222
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors

Abstract

A control circuit providing automatic data terminal answering in response to a ring signal request by a remote machine. The circuit includes: logic circuitry for initiating operation of the terminal and placing the terminal off hook in response to a ring signal; circuitry for monitoring the transmission carrier and the data signal for switching the terminal on hook if the carrier or data transmission ceases for selected periods of time; and circuitry for returning the terminal on hook if a ring signal is not followed by data transmission within a suitable time period. Answer and originate modes are also selectable.

Claims

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.

2. A circuit according to claim 1 wherein said logic circuit means further comprises:

transmission monitoring logic means having inputs connected to said carrier loss timing means and said long mark timing means and having an output for shifting from a first state to a second state for maintaining the terminal in said enabled condition so long as said carrier loss timing means and said long mark timing means are both in their respective said first states.

3. A circuit according to claim 2 wherein a. a manual/automatic switch is provided for alternatively selecting an automatic and a manual operative mode for said terminal;

and b. a first '"'"''"'"''"'"''"'"'or'"'"''"'"''"'"''"'"' gate means has inputs connected to said manual/automatic switch, to the output of said and gate means, and to the output of said monitoring means, said first '"'"''"'"''"'"''"'"'or'"'"''"'"''"'"''"'"' gate means having an output for shifting from a first state to a second state and thereby enabling operation of said terminal whenever said monitoring means is in its second state, whenever said '"'"''"'"''"'"''"'"'and'"'"''"'"''"'"''"'"' gate means is in its second state, and whenever said manual/automatic switch is switched tO manual operation.

4. A circuit according to claim 3 wherein a. an originate/answer switch is provided for switching the terminal into its enabled condition without regard to the presence of a ring signal;

and b. a second '"'"''"'"''"'"''"'"'or'"'"''"'"''"'"''"'"' gate means is provided having inputs connected to said originate/answer switch and to the output of said first '"'"''"'"''"'"''"'"'or'"'"''"'"''"'"''"'"' gate means for enabling operation of said terminal whenever said first '"'"''"'"''"'"''"'"'or'"'"''"'"''"'"''"'"' gate means is in its second state and whenever said originate/answer switch is switched to its originate condition.