Wireless multi-head smoke detector system

• US 4,160,246 A
• Filed: 10/03/1977
• Issued: 07/03/1979
• Est. Priority Date: 10/03/1977
• Status: Expired due to Term

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: Fairchild Camera and Instrument Corporation (ON Semiconductor Corporation)
• Inventors: Martin, Stephen M., Miller, Ralph P.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US05/839,074
• Time in Patent Office: 638 Days
• Field of Search: 340/237 S, 340/249, 340/224, 340/420, 340/421, 340/630, 340/636, 340/539, 356/207, 250/574, 250/575
• US Class Current: 340/630
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 25/10 using wireless transmission systems G08B25/009 takes precedence

Abstract

A wireless smoke detector apparatus including at least one detector/transmitter unit and a receiver/annunciator unit. The detector/transmitter having a pulsed infrared radiation source, a photodetector having an optical axis angularly intersecting the axis of the radiation source for detecting radiation scattered by smoke particles and a transmitter responsive to the output of the detector for transmitting a unique receiver/annunciator actuating signal which is distinguishable by the receiver/annunciator from other actuating signals.

Claims

1. A detector/transmitter unit for a wireless smoke detector system comprising at least one detector/transmitter unit and a receiver/annunciator unit for producing alarm signals in response to actuating signals transmitted by radio frequency waves from said at least one detector/transmitter unit, said detector/transmitter unit comprising:

pulse means for repetitively generating a clock signal;

an infrared source for repetitively generating a beam of infrared radiation responsive to said clock signal and substantially coincident in time with said clock signal;

a photodetector having a collection axis angularly intersecting said beam for detecting infrared radiation reflected from smoke particles encountered by said beam and for developing an infrared detection signal whenever smoke particles are detected;

low battery voltage detecting means for monitoring the voltage across a power source for the detector/transmitter unit and for developing a low battery signal whenever said voltage falls below a predetermined level; and

transmitter means (1) for generating a first actuating signal for said receiver/annunciator unit in response to both said clock signal and said low battery signal, and (2) for generating a second actuating signal for said receiver/annunciator in response to both said clock signal and said detection signal.

2. A detector/transmitter unit according to claim 1 wherein said collection axis angularly intersects said beam at an angle in the range of 115°

to 135°

.

3. A detector/transmitter unit according to claim 2 wherein said transmitter means includes:

first gate means responsive to said clock signal and said low battery signal for generating a first gate signal for a first time period following the occurrence of said clock signal;

amplifier means for amplifying said detection signal to produce an amplified signal;

second gate means responsive to said clock signal and said amplified signal for generating a second gate signal for a second time period following the occurrence of both said clock signal and said amplified signal; and

a radio frequency oscillator (1) responsive to said first gate signal for generating said first actuating signal substantially coincident in time with said first gate signal and (2) responsive to said second gate signal for generating said second actuating signal substantially coincident in time with said second gate signal.

4. A detector/transmitter unit according to claim 3 wherein:

said first gate means is a first flip-flop device having a clock input for receiving said clock signal, a set input for receiving said low battery signal, and an output for generating said first gate signal; and

said second gate means is a second flip-flop device having a clock input for receiving said clock signal, a data input for receiving said amplified signal, and an output for generating said second gate signal.

5. A detector/transmitter unit according to claim 3 wherein said transmitter means further includes a radio frequency amplifier for amplifying said first and second actuating signals to extend the range of said detector/transmitter unit.

6. A detector/transmitter unit according to claim 3 wherein said first time period is less than the time between successive clock signals generated by said pulse means and wherein said second time period is substantially equal to the time between successive clock signals generated by said pulse means, whereby the transmission period for said first actuating signal is equal to only a portion of the time between successive clock signals and whereby the transmission period for said second actuating signal is substantially equal to the entire time between successive clock signals.

7. A receiver/annunciator unit for a wireless smoke detector system according to claim 6 wherein said receiver/annunciator unit is activated to produce alarm signals only for time periods substantially equal to said transmission periods.

8. A detector/transmitter unit according to claim 2 wherein said transmitter means includes modulator means for distinctly modulating said first and second actuating signals to differentiate them from actuating signals developed by other detector/transmitter units.

9. A detector/transmitter unit according to claim 8 wherein said modulator means frequency modulates said first and second actuating signals at a superaudio rate.