Receiver for audible alarm
First Claim
1. Apparatus to detect sonic signals within a predetermined range of frequencies comprising an electret microphone with integral FET impedance converter for receiving the sonic signal, band-pass filter means connected to the output of said electret microphone, AGC means connected to the output of said filter means and producing an AGC bias voltage which is applied to the FET to control the sensitivity of said electret microphone, and means connected to the output of said filter means for producing a defined response to the presence of the sonic signal.
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Accused Products
Abstract
A receiver to detect the audio tone emitted by an activated smoke alarm. The receiver employs an electret condenser microphone to monitor ambient sound. The output of the microphone is applied to an active band-pass filter and then to a PLL tone decoder. The PLL is tunable to provide maximum sensitivity to the frequency of the tone. The microphone is the gain controllable element in an AGC system that acts to keep received signals at a constant level. This insures that all devices operate linearly.
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Citations
9 Claims
- 1. Apparatus to detect sonic signals within a predetermined range of frequencies comprising an electret microphone with integral FET impedance converter for receiving the sonic signal, band-pass filter means connected to the output of said electret microphone, AGC means connected to the output of said filter means and producing an AGC bias voltage which is applied to the FET to control the sensitivity of said electret microphone, and means connected to the output of said filter means for producing a defined response to the presence of the sonic signal.
- 4. A receiver to detect the audio tone emitted by an activated smoke alarm comprising transducer means adapted to receive sound energy and converting the same to an electrical signal, band-pass filter means electrically coupled to said transducer means and acting sharply to attenuate electrical signals above and below a defined bandwith, signal amplifier means electrically connected to the output of said filter means for amplifying the electrical signals passed through said filter means, phase locked loop means electrically connected to the output of said amplifier means and adapted to lock onto the amplified electrical signal representing the audio tone and electrically indicate the presence thereof, and means for filtering out the ring of a telephone, the last-mentioned means coupled to the output of said PLL and responsive to the momentary unlocking thereof induced between telephone rings.
- 7. A receiver for detecting an audio signal that falls within a predetermined range of frequencies comprising microphone means for monitoring the presence of the audio signal, signal amplifier means connected to the output of said microphone means for boosting the output thereof a given amount, phase locked loop tone decoder means coupled to the output of said amplifier means, said tone decoder means adapted to lock onto the audio signal when the same is present at the output of said amplifier means and indicate such presence by a change in state at the output of said tone decoder means, said tone decoder means being tunable over a narrow frequency bend whereby the same can be tuned to the frequency of the audio signal thereby providing maximum sensitivity thereto, and delay means coupled to the output of said tone decoder means, said delay means including a resettable timer that when activated by the output of said tone decoder means has a delay period that is, at least, approximately three seconds long and including nearly instantaneous reset means, the last-mentioned means adapted to reset the timer when said tone decoder means momentarily unlocks.
Specification