AUTOMATIC MOTOR SHUTOFF NETWORKS FOR SIGNAL SEEKING RECEIVERS

• US 3,584,307 A
• Filed: 10/24/1967
• Issued: 06/08/1971
• Est. Priority Date: 10/24/1967
• Status: Expired due to Term

• Current Assignee: David W. Hewie
• Original Assignee: David W. Hewie
• Inventors: Hewie, David W.
• Application Number:
  US04/677,673
• Time in Patent Office: 1,323 Days
• US Class Current: 455/163.1
• CPC Class Codes: H03J 7/305 in which an automatic frequency control circuit is brought in action after the scanning action has been stopped

Abstract

A signal seeking receiver has variable tuning means for varying the tuning of the receiver and a motor drivingly connected to the tuning means. An automatic shutoff network automatically turns off the motor when the receiver is tuned to the frequency of a signal being received by the receiver and of a strength greater than a minimum predetermined signal strength. The automatic shutoff network is a monostable multivibrator that automatically turns off the motor after it has been operating for a predetermined period of time without the receiver having been tuned to one such received signal during the period.

Claims

1. In a signal seeking receiver of a type having variable tuning means for varying the tuning of said receiver, a motor drivingly connected to said tuning means, whereby the tuning of said receiver can be changed by operation of said motor, and an automatic shutoff network for automatically turning off said motor when said receiver is tuned to the frequency of a signal being received by said receiver and of a strength greater than a minimum predetermined signal strength;

the improvement wherein said automatic shutoff network comprises a monostable multivibrator network adapted to turn off said motor after said motor has been operating for a predetermined period of time without said receiver having been tuned to one of said received signals during said period, said monostable multivibrator network comprising first and second transistors interconnected such that when either of said transistors is turned on or off, the other of said transistors is kept turned off or on respectively until the state of conduction of the first-mentioned transistor changes, said second transistor being turned on being a stable state of said monostable multivibrator and said first transistor being turned on being an unstable state of said monostable multivibrator;

said signal seeking receiver also including means for supplying a first signal to said second transistor when said receiver is tuned to the frequency of a signal being received by said receiver to turn on said second transistor when said first signal is of a strength greater than a minimum predetermined signal strength;

means connecting said first transistor in a circuit through which current required in order for said motor to operate must pass, whereby when said first transistor is turned off, said current is unable to flow through said circuit and said motor ceases operating;

means for supplying a biasing voltage to said second transistor to turn on said second transistor when said motor is not operating; and

switching means having first and second different states and which initiate operation of said motor when in said second state.

2. The invention according to claim 1 wherein said first and second transistors each have base, collector and emitter electrodes, and wherein said monostable multivibrator network also includes first, second, third and fourth resistors, a first capacitor and a coil of a relay having contacts in circuit with sAid motor, said first resistor being connected between said means for supplying said biasing voltage and said collector electrode of said second transistor, said second resistor being connected between said means for supplying said biasing voltage and said base electrode of said second transistor, said third and fourth resistors being connected in series circuit with each other between said collector electrode of said second transistor and a terminal at a reference potential, said third and fourth resistors having a common terminal connected to said base electrode of said first transistor, said coil being connected between said means for supplying said biasing voltage and said collector electrode of said first transistor, said first capacitor being connected between said collector electrode of said first transistor and said base electrode of said second transistor, and means connecting said emitter electrodes of said first and second transistors and said terminal at said reference potential.

3. The invention according to claim 2 wherein said monostable multivibrator network includes first and second diodes, said first diode being connected in a series circuit with said coil between said means for supplying said biasing voltage and said collector electrode of said first transistor and also in a series circuit with said coil and said first capacitor between said means for supplying said biasing voltage and said base electrode of said second transistor, said second diode also being connected in the last-mentioned series circuit and in another series circuit with said second resistor between said means for supplying said biasing voltage and said base electrode of said second transistor.

4. The invention according to claim 3 wherein said monostable multivibrator network includes a fifth resistor connected in series circuit with said first capacitor between said collector electrode of said first transistor and said second diode, and a second capacitor connected between said base electrode of said second transistor and said terminal at said reference potential.

5. The invention according to claim 1 wherein said means for supplying said first signal to said second transistor includes a signal input terminal, a third diode and means connecting said third diode between said signal input terminal and said second transistor;

said signal seeking receiver also including a fourth diode connected to said third diode but with reverse polarity, and means for supplying a voltage to said fourth diode to reverse bias said fourth diode.

6. The invention according to claim 5 wherein said fourth diode is connected between said third diode and a terminal at a reference potential.

7. The invention according to claim 6 including a sixth resistor, said sixth resistor being connected between said fourth diode and said terminal at said reference potential, said means for supplying a voltage to said fourth diode to reverse bias said fourth diode including said sixth resistor and a DC path including a switch connected between said sixth resistor and said means for supplying said biasing voltage.

8. The invention according to claim 7 wherein said first and second transistors each have base, collector and emitter electrodes, and wherein said monostable multivibrator network also includes first, second, third and fourth resistors, a first capacitor and a coil of a relay having contacts in circuit with said motor, said first resistor being connected between said means for supplying said biasing voltage and said collector electrode of said second transistor, said second resistor being connected between said means for supplying said biasing voltage and said base electrode of said second transistor, said third and fourth resistors being connected in series circuit with each other between said collector electrode of said second transistor and a terminal at a reference potential, said third and fourth resistors having a common terminal connected to said base electrode of said first transistor, said coiL being connected between said means for supplying said biasing voltage and said collector electrode of said first transistor, said first capacitor being connected between said collector electrode of said first transistor and said base electrode of said second transistor, and means connecting said emitter electrodes of said first and second transistors and said terminal at said reference potential.

9. The invention according to claim 8 wherein said monostable multivibrator network includes first and second diodes, said first diode being connected in a series circuit with said coil between said means for supplying said biasing voltage and said collector electrode of said first transistor and also in a series circuit with said coil and said first capacitor between said means for supplying said biasing voltage and said base electrode of said second transistor, said second diode also being connected in the last-mentioned series circuit and in another series circuit with said second resistor between said means for supplying said biasing voltage and said base electrode of said second transistor.