End-of-transmission keying device

• US 5,212,812 A
• Filed: 10/01/1990
• Issued: 05/18/1993
• Est. Priority Date: 10/01/1990
• Status: Expired due to Fees

• Current Assignee: Mr Jiggs CB Development Incorporated
• Original Assignee: Mr Jiggs CB Development Incorporated
• Inventors: Dutton, Roy F.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Woldu, Almaz
• Application Number:
  US07/590,943
• Time in Patent Office: 960 Days
• Field of Search: 455/73, 455/84, 455/79, 455/116, 455/115, 455/68, 455/69, 455/58, 375/68, 379/58
• US Class Current: 455/73
• CPC Class Codes: H04B 1/46 by voice-frequency signals; by pilot signals

Abstract

A device automatically re-keys a transmitter after a transmission ceases, and thereafter transmits a preselected audio signal. The device has a key-open sensor for sensing the end of a transmission and for initiating the audio signal. A keying circuit is controlled by the sensor to re-key the transmitter. An audio sensor senses the presence of the audio signal and controls the keying circuit to un-key the transmitter when the audio signal ceases.

Claims

1. A device for automatically re-keying a transmitter after a transmission ceases, and for thereafter transmitting a preselected audio signal comprising:

a) key-open sensing means having an input to a first transistor connected to said transmitter, axis transistor turned on when said transmission ceases to thereby produce a trigger signal, a latch circuit connected to said first transistor, said trigger signal setting a HIGH at an output of said latch circuit, and a trigger signal output for providing an indicating signal for said preselected audio signal;

b) auxiliary keying means responsive to said key-open sensing means for re-keying said transmitter; and

c) audio sensing means connected to said latch circuit for sensing presence of said preselected audio signal, and for resetting said latch circuit to open said auxiliary keying means thereby un-keying said transmitter.

2. The device as defined in claim 1 in which said auxiliary keying means includes a normally OFF second transistor connected to said output of said latch circuit, and to said transmitter wherein said HIGH turns said transistor ON for re-keying said transmitter.

3. The device as defined in claim 1 in which said audio sensing means includes:

a) a connection to said first transistor for placing an inhibit signal thereon

b) an input connected to receive said preselected audio signal when present;

c) a rectifier circuit for producing a dc signal from said audio sensing means input; and

d) a comparator connected to said rectifying circuit and to said latch circuit wherein said dc signal turns said comparator OFF, and cessation of said preselected audio signal causes said comparator to turn ON, resetting said latch circuit producing a LOW at said latch circuit output.

4. The device as defined in claim 3 in which said audio sensing means further includes an audio amplifier for providing an amplified signal to said rectifying circuit, and an input for receiving said trigger signal.

5. The device as defined in claim 3 in which said audio rectifier circuit further includes a time delay circuit for maintaining said comparator OFF during pauses in said audio signal.

6. A device for automatically re-keying a transmitter after a transmission ceases, and for thereafter transmitting a preselected audio signal comprising:

a) key-open sensor having a first transistor having an input for connecting to said transmitter, said transistor turned on when said transmission ceases for producing a trigger signal;

b) a latch circuit connected to said first transistor, said trigger signal setting a HIGH at an output of said latch circuit, and a trigger signal output for providing an initiating signal for said preselected audio signal;

c) a keying circuit having a normally OFF second transistor connected to said output of said latch circuit, and to said transmitter wherein said HIGH turns said transistor ON for rekeying said transmitter; and

d) an audio sensing circuit having a connection to said first transistor for placing an inhibit signal thereon, an input connected to receive said preselected audio signal when present, a rectifier circuit for producing a dc signal from said audio sensing means input, and a comparator connected to said rectifying circuit and to said latch circuit wherein said dc signal turns said comparator OFF, and cessation of said preselected audio signal causes said comparator to turn ON, resetting said latch circuit producing a LOW at said latch circuit output.

7. The device as defined in claim 6 in which said audio sensing circuit further includes an audio amplifier for providing an amplified signal to said rectifying circuit, and an input for receiving said trigger signal.