Battery-operated receiver for wireless audible indication system

• US 5,757,267 A
• Filed: 12/12/1995
• Issued: 05/26/1998
• Est. Priority Date: 07/29/1994
• Status: Expired due to Fees

• Current Assignee: Lamson & Sessions Company (ABB Limited)
• Original Assignee: Dimango Products Corp (ABB Limited)
• Inventors: Xydis, Thomas G.
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): Pope, Daryl C.
• Application Number:
  US08/570,828
• Time in Patent Office: 896 Days
• Field of Search: 340/330, 340/539, 340/825.69, 340/825.44, 340/825.72, 340/825.48, 340/384.71, 340/384.72, 340/384.73, 340/692, 341/176, 455/336, 455/339, 455/38.3
• US Class Current: 340/330
• CPC Class Codes: G08B 3/10 using electric transmission; using electromagnetic transmission

Abstract

A wireless audible indication system comprising a transmitter and a receiver. An embodiment of the transmitter includes a crystal oscillator which produces a signal having a predetermined audio frequency. A duty cycle limiting circuit limits the duty cycle of the oscillator signal to be less than 25%. The limited duty cycle signal is applied to a radio frequency oscillator to produce an amplitude modulated radio frequency signal. An embodiment of the receiver includes a superregenerative detector which provides wide band detection of transmissions about a carrier frequency. A signal processing circuit formed by a cascade of a crystal filter stage, an amplifier/comparator stage, and a detector stage, processes the signal from the superregenerative detector. A sound generator integrated circuit, which generates an audible signal indicative of reception of a transmitted signal, is coupled to the signal processing circuit. Another embodiment of the receiver includes two parallel signal processing paths having different crystal filter stages, which allows use with two different transmitters.

Claims

1. A receiver for use in an audible indication system with a corresponding transmitter which transmits a radio frequency signal, the receiver powered by a battery source, the receiver comprising:

a radio frequency detector which produces a first signal upon receiving the radio frequency signal from the corresponding transmitter;

a signal processing circuit, coupled to the radio frequency detector, which processes the first signal to form a second signal, wherein the signal processing circuit includes a CMOS device which contains a plurality of MOS field effect transistors having a threshold voltage; and

a sound generator, coupled to the signal processing circuit, which generates an audible indication when the second signal is indicative of reception of the radio frequency signal;

wherein the CMOS device is powered at a first voltage near to the threshold voltage of the MOS field effect transistors in the CMOS device.

2. The receiver of claim 1 wherein the first voltage is near 3 volts.

3. The receiver of claim 1 wherein the CMOS device includes an inverter gate formed by at least one of the plurality of MOS field effect transistors.

4. The receiver of claim 1 wherein the CMOS device includes a NAND gate formed by at least two of the plurality of MOS field effect transistors.

5. The receiver of claim 1 wherein the radio frequency detector is powered at the first voltage.

6. The receiver of claim 1 wherein the sound generator is powered at a second voltage, wherein the second voltage is greater than the first voltage.

7. The receiver of claim 1 further comprising a voltage regulator coupled to the battery source and to the CMOS device, wherein the voltage regulator regulates the battery source to provide a source of the first voltage for powering the CMOS device.

8. The receiver of claim 7 wherein the battery source has a voltage near 6 volts.

9. A receiver for use in an audible indication system with a corresponding transmitter which transmits a radio frequency signal, the receiver powered by a battery source, the receiver comprising:

a radio frequency detected which produces a first signal upon receiving the radio frequency signal from the corresponding transmitter;

a power supply circuit which produces a first voltage source and a second voltage source from the battery source, wherein the second voltage source has a voltage greater than the first voltage source, the power supply circuit including a voltage regulator which regulates the battery source to produce the first voltage source;

a signal processing circuit, coupled to the radio frequency detector, which processes the first signal to form a second signal, the signal processing circuit including a CMOS device which contains a plurality of MOS field effect transistors having a threshold voltage, wherein the signal processing circuit is powered by the first voltage source, and the first voltage source is near the threshold voltage; and

a sound generator, coupled to the signal processing circuit, which generates an audible indication when the second signal is indicative of reception of the radio frequency signal, wherein the sound generator is powered by the second voltage source.

10. The receiver of claim 9 wherein the first voltage source is regulated to be near 3 volts.

11. The receiver of claim 9 wherein the battery source has a voltage near 6 volts.

12. The receiver of claim 9 wherein the second voltage source has a voltage near 5.4 volts.