US 4,332,977 A · Teletypewriter privacy system

Abstract

1. A teletypewriter privacy system comprising a first and a second pair of terminals responsive to printing-telegraphy signals having start bauds; means for generating program signals having a fixed timing relationship with the start bauds of said telegraphy signals; a mixer circuit coupled between said terminals, and responsive to said program signals; said mixer circuit including a first switch coupled to said first pair of terminals, and a second switch coupled to said second pair of terminals, means responsive to a start baud at said first pair of terminals for maintaining said first switch operative to couple said first pair of terminals to said mixer circuit for one telegraph character, means responsive to a start baud at said second pair of terminals for maintaining said second switch operative to couple said second pair of terminals to said mixer circuit for one telegraphy character, first polarized switch means responsive to the telegraphy signal at the first pair of terminals and the program signal for selectively activating said second switch, and second polarized switch means responsive to the telegraphy bauds at the second pair of terminals and the program signal for selectively activating said first switch. 19. In combination, an electrical switching circuit for generating four pseudo-random binary electrical signals that correspond to W, X, Y and Z, and another electrical circuit for combining, through logical OR gates, said electrical signals to generate a further electrical signal representing WXYZ+XY+Z W, for use as a key for encoding a communication signal.

Claims21

Dependent claims

A teletypewriter privacy system comprising a first and a second pair of terminals responsive to printing-telegraphy signals having start bauds;

means for generating program signals having a fixed timing relationship with the start bauds of said telegraphy signals;
a mixer circuit coupled between said terminals, and responsive to said program signals;
said mixer circuit including a first switch coupled to said first pair of terminals, and a second switch coupled to said second pair of terminals, means responsive to a start baud at said first pair of terminals for maintaining said first switch operative to couple said first pair of terminals to said mixer circuit for one telegraph character, means responsive to a start baud at said second pair of terminals for maintaining said second switch operative to couple said second pair of terminals to said mixer circuit for one telegraphy character, first polarized switch means responsive to the telegraphy signal at the first pair of terminals and the program signal for selectively activating said second switch, and second polarized switch means responsive to the telegraphy bauds at the second pair of terminals and the program signal for selectively activating said first switch.

A teletypewriter privacy system comprising a first and a second pair of input terminals responsive to telegraphy signals having start bauds;

means for generating a program signal;
a mixer connected between said terminals;
said mixer comprising a line signal relay having contacts normally coupled between the first pair of terminals and the remainder of the mixer, a teletypewriter signal relay having contacts normally coupled between the second pair of terminals and the remainder of the mixer, a source of power, a line trigger relay, a teletypewriter trigger relay, a polarized bistable pulse control relay, a circuit reversing polarized bistable relay, a teletypewriter repeater relay, a line repeater relay, said line trigger relay having contacts for applying said source of power to energize said reversing relay into a receive state and said pulse control relay into an operate state in response to a start baud at said first terminals, said reversing and pulse control relays when energized into said states having contacts connected to said source of power for locking said line signal relay into its normal state, said teletypewriter trigger relay having contacts for applying said source of power to energize said reverse relay into a transmit state and said pulse control relay into an operate state in response to a start baud at said second terminals, said reverse and pulse control relays when energized into said last named states having contacts connected to said source of power for locking said teletypewriter signal relay into its normal state, means for energizing said line repeater relay in response to the bauds applied to said first pair of terminals, a control circuit responsive to said program signal for energizing said teletypewriter signal relay to a selective polarity, said control circuit including the contacts of said line repeater relay, means for energizing said teletypewriter repeater relay in response to the bauds applied to said second pair of terminals, and another control circuit responsive to said program signal for energizing said line signal relay to a selective polarity, said another control circuit including the contacts of said teletypewriter repeater relay.

Dependencies are inferred from the claim text.

Teletypewriter privacy system

Life of this patent

Teletypewriter privacy system

Life of this patent

Abstract

Claims21