Acoustical switch

• US 3,970,987 A
• Filed: 05/31/1974
• Issued: 07/20/1976
• Est. Priority Date: 08/17/1972
• Status: Expired due to Term

• Current Assignee: Signal Science, Inc. (ITT, Inc.)
• Original Assignee: Signal Science, Inc. (ITT, Inc.)
• Inventors: Kolm, Eric A.
• Primary Examiner(s): Wilbur, Maynard R.
• Assistant Examiner(s): Blum, T. M.
• Application Number:
  US05/474,875
• Time in Patent Office: 781 Days
• Field of Search: 340/15, 340/171 R, 340/16 C, 340/310 R, 325/37, 307/315, 178/DIG. 15, 353/105, 353/106, 353/122
• US Class Current: 367/135
• CPC Class Codes: G01S 1/72 using ultrasonic, sonic or infrasonic waves

Abstract

An acoustical switch is actuated from a remote location by a sound generator such as an ultrasonic whistle. The switch includes a special tuned signal receiver coupled with an amplifier having a frequency selective feedback network. The output of the amplifier is an a.c. signal which is applied to a bistable circuit which, in one state, energizes a relay to turn on an appliance connected to the switch and, in its other state, turns the appliance off.

Claims

1. An acoustical switch comprising

A. an acoustical transducer for converting sounds into AC signals,

B. an amplifying circuit connected to amplify a selected band of AC signals received from said transducer in the upper audible or ultrasonic frequency range,

C. means for connecting said switch to a power source, and

D. a switching circuit

3. The acoustical switch defined in claim 1

A. wherein the amplifier circuit has relatively high gain, and

B. further including means for adjusting said gain.

4. The acoustical switch defined in claim 1 wherein the amplifier circuit and switching circuit are comprised of a single monolithic dual operational amplifier.

5. The acoustical switch defined in claim 1 and further including

A. a whistle which emits an acoustical signal in said range when blown, and

B. means associated with the whistle for blowing it.

6. The acoustical switch defined in claim 1 wherein the switching circuit also includes an electronic switch which is turned on when the amplifier output voltage is at one extreme of its fluctuation and is turned off when that voltage is at the other extreme of its fluctuation.

7. The acoustical switch defined in claim 5 wherein the electronic switch includes a pair of transistors connected in a Darlington configuration with the amplifier output voltage controlling the voltage at the base of the first transistor.

8. The acoustical switch defined in claim 5 and further including means in circuit with the amplifier for shunting to ground transient output signals from the amplifier so that the switch is only responsive to acoustical signals of a predetermined duration.

9. The acoustical switch defined in claim 1 wherein the desensitizing means includes a parallel-connected resistor and capacitor in the coupling means which holds the other amplifier input beyond a selected voltage level until the charge produced on the capacitor when the amplifier output changes discharges through the resistor so that the switch cycles only in response to acoustical signals which are spaced apart in time by a selected time interval.

10. The acoustical switch as defined in claim 8 and further including a low pass filter connected between the transducer and the operational amplifier to eliminate ambient noise spikes.

11. The acoustical switch as defined in claim 8 and further including means for altering the resistance and/or capacitance of the coupling means to alter the time constant of the switching means.

12. The acoustical switch as defined in claim 10 and wherein the time constant is selected so that the switching circuit is monostable.

15. The switch defined in claim 12 wherein the switching circuit is also arranged to alternately connect the power source to and disconnect it from said device upon the occurrence of successive said acoustical signals.

16. The switch defined in claim 12 wherein the switching circuit has a selected time constant so that the switch connects the power source to the device only for the selected period of time following the first acoustical signal.

17. The acoustical switch defined in claim 12 wherein the transducer comprises a piezoelectric ceramic bimorph tuned to a frequency in the upper audible or lower ultrasonic range, said bimorph producing a relatively strong AC signal when excited by said frequency.

18. The acoustical switch defined in claim 15 wherein the bimorph is arranged to vibrate in the flexural mode.

19. The acoustical switch defined in claim 15 and further including

A. a stationary base,

B. a flexible resilient pad, and

C. means for securing the bimorph flush against the pad and the pad flush against the base.

20. The acoustical switch defined in claim 17 wherein the pad is a strip of double-faced adhesive foam tape.

2. operative in response to the AC output of said amplifying circuit, andarranged to alternately connect said power source to and disconnect it from an appliance upon the occurrence of successive outputs from said transducer, said switching circuit including

a. an operational amplifier,

b. means for applying the AC signal to one input of the amplifier,

c. means for coupling the output voltage of the amplifier to another input thereof so that the output voltage tends to fluctuate with the a.c. signal, and

d. means associated with the amplifier for temporarily desensitizing the switching circuit during selected half-cycles of the AC signal so that the amplifier output voltage remains substantially at the value it first changed to on commencement of the AC signal.

13. An acoustical switch comprising

A. a piezoelectric transducer tuned to a selected frequency in the upper audible or lower ultrasonic frequency range so as to produce a strong AC signal when acoustically excited at that frequency,

B. high gain amplifying circuit connected to amplify the AC signal from the transducer,

C. means for connecting the switch to a power source,

D. means for connecting said switch to a power consuming device, and

E. a switching circuit,

14. operative in response to the AC output of said amplifying circuit, andarranged to connect the power source to the device upon the occurrence of a first said signal, said switching circuit including

a. an amplifier,

b. means for applying the AC signal as one input to the amplifier,

c. means for applying the amplifier output as another input to the amplifier, and

d. means associated with the amplifier for temporarily desensitizing the switching circuit during selected half-cycles of the AC signal so that the amplifier output voltage remains substantially at the value it first changed to upon commencement of the AC signal.