Integrated fully supervised fire alarm system

Abstract

A low voltage audio fire alarm system fully integrated in a paging and music speaker system. The alarm circuits including pull-boxes and automatic fire, smoke and heat detection apparatus and the audio circuits are fully and continuously supervised against component failure by means of a plurality of current responsive relays. The audio path including the speaker system and associated amplifiers is continuously monitored by a low level supersonic 26KC signal. Fail-safe features utilizing multi-contact switches and relays are incorporated throughout the system to prevent inadvertent silencing of alarms in the absence of an alarm condition.

What is claimed is: 
     
       1. A fire alarm system comprising: an audio circuit including a speaker; a source of supervisory signals normally coupled to said audio circuit for detecting malfunctions in said audio circuit; a source of audio alarm signals; an alarm indicating circuit for indicating an alarm condition; switch means coupled to said source of supervisory signals and said source of audio alarm signals and responsive to said alarm indicating circuit for selectively decoupling said source of supervisory signals from said audio circuit and coupling said source of audio alarm signals to said audio circuit for broadcasting an audible alarm through said speakers in response to an indication from said alarm indicating circuit of the existence of an alarm condition. 
     
     
       2. A fire alarm system according to claim 1 wherein said source of supervisory signals is an oscillator for generating a supersonic signal and further comprising: relay means coupled to said audio circuit and said oscillator including means responsive to said supersonic signals for maintaining said relay means, normally energized and means coupled to said relay means for indicating when said relay means is in a de-energized state for indicating a malfunction in either said audio circuit or said oscillator. 
     
     
       3. A fire alarm system according to claim 2 wherein said oscillator is adapted to output a supersonic signal of approximately 26KC. 
     
     
       4. A fire alarm system according to claim 3 wherein said supersonic signal is approximately 26KC and the output power of said oscillator is relatively low. 
     
     
       5. A fire alarm system according to claim 1 wherein said source of audio alarm signals is a tone generator for generating an audible alarm signal and further comprising: relay means coupled to said tone generator including means responsive to the output of said tone generator for maintaining said relay means normally energized and means coupled to said last named relay means for indicating when said last named relay means is in a de-energized state for indicating a malfunction in said tone generator. 
     
     
       6. A fire alarm system according to claim 1 wherein said alarm indicating circuit includes switch means adapted to be switched from a first mode of operation to a second mode of operation to indicate an alarm condition; and further comprising: relay means responsive to said switch means operable to be changed from a normally de-energized state to an energized state when said switch means is switched to its second mode of operation and wherein said relay means serves to control said switch means coupled to said source of supervisory signals and said source of audio alarm signals. 
     
     
       7. A fire alarm system according to claim 6 further comprising: a source of power; a normally energized relay means coupled in series with said source of power and said alarm indicating circuit for monitoring the continuity of said alarm indicating circuit and means coupled to said relay means for indicating when said relay means is de-energized for indicating a break in continuity in said alarm indicating circuit. 
     
     
       8. A fire alarm system comprising a source of dc power; an oscillator for generating a supersonic supervisory signal coupled to said source; a tone generator for generating an audible alarm signal coupled to said source; an audio circuit including a speaker; an alarm relay means, an alarm condition indicating circuit coupled to said source and operable to control said alarm relay means for indicating the existence of an alarm condition, switch means, coupled to said oscillator and said tone generator and responsive to said alarm relay means for selectively de-coupling said oscillator from said audio circuit and coupling said tone generator to said audio circuit for transmitting an audible alarm through said speaker; a first relay coupled to said source of dc power for indicating when said source is producing less than a predetermined amount of power; a second relay coupled to said oscillator and said audio circuit for indicating when said oscillator is failing to generate said supervisory signal and said audio circuit lacks continuity; a third relay coupled to said tone generator and said oscillator for indicating when said tone generator fails to generate said alarm signal and said oscillator is improperly installed in said fire alarm system; a fourth relay coupled to said alarm condition indicating circuit for indicating when said alarm condition indicating circuit lacks continuity; alarm reset switch means having an alarm and a silence mode coupled to said alarm relay means for selectively silencing said audible alarm during the existence of an alarm condition; and means coupled to said alarm reset switch means for providing a trouble signal when said alarm reset switch means is placed in a silence mode in the absence of an alarm condition. 
     
     
       9. A fire alarm system comprising: a source of power, a supersonic signal generator coupled to said source; a tone generator coupled to said source; first switch means coupled to the outputs of said supersonic signal generator and said tone generator; an audio circuit including a speaker coupled to said first switch means, said first switch means serving to selectively coupled said supersonic signal generator and said tone generator to said audio circuit; first relay means coupled to said first switch means; and second switch means coupled to said relay means and operable for changing said first relay means from a de-energized state to an energized state for switching said first switch means. 
     
     
       10. A fire alarm system according to claim 9 further comprising: a second relay means coupled to said supersonic signal generator and said audio circuit for detecting malfunctions in said supersonic signal generator and said audio circuit and means coupled to said second relay means for indicating a detected malfunction. 
     
     
       11. A fire alarm system according to claim 10 further comprising: third relay means coupled to said tone generator for detecting malfunctions in said tone generator, and means coupled to said third relay means for indicating a detected malfunction. 
     
     
       12. A fire alarm system according to claim 11 further comprising: a fourth relay means coupled in series with said second switch means and said first relay means for detecting malfunctions in said second switch means and said first relay means; and means coupled to said fourth relay means for indicating a detected malfunction. 
     
     
       13. A fire alarm system according to claim 12 further comprising: third switch means coupled in series with said first relay means and said second switch for disconnecting said first relay means from said second switch means; and means coupled to said third switch means for indicating when said first relay means is disconnected from said second switch means in the absence of any alarm condition or malfunction in said fire alarm system. .Iadd. 14. An audio alarm system comprising: an audio circuit, said audio circuit including an amplifying means having an input means and an output means; a speaker circuit coupled to said output means of said amplifying means in said audio circuit; means for coupling said audio and said speaker circuits to a first source of audio frequency signals; means forming an oscillator for generating supervisory signals having an inaudible frequency; means for coupling said generating means to said input means of said audio circuit and said speaker circuit, said coupling means including means for superimposing said supervisory signals and said audio frequency signals from said first source in said amplifying means of said audio circuit and said speaker circuit; means responsive to said supervisory signals coupled to said output means of said amplifying means for detecting malfunctions in said amplifying means and said speaker circuit; a second source of audio frequency signals for generating audio frequency alarm signals; an alarm-indicating circuit for indicating the existence of an alarm condition; and means responsive to an indication of the existence of an alarm condition from said alarm-indicating circuit for coupling said source of audio frequency alarm signals to said audio circuit for broadcasting said audio frequency alarm signals over said speaker circuit. .Iaddend..Iadd. 15. An audio alarm system according to claim 14 further comprising: a means coupled to said alarm indicating circuit for detecting malfunctions in said alarm indicating circuit. .Iaddend.