FIRE ALARM SYSTEMS EQUIPPED WITH CIRCUIT MONITORING DEVICES

• US 3,678,510 A
• Filed: 10/05/1970
• Issued: 07/18/1972
• Est. Priority Date: 05/09/1966
• Status: Expired due to Term

• Current Assignee: Andreas Scheidweiler, Beat Walthard, Max Kuhn
• Original Assignee: Andreas Scheidweiler, Beat Walthard, Max Kuhn
• Inventors: Walthard, Beat, Scheidweiler, Andreas, Kuhn, Max
• Primary Examiner(s): Habecker, Thomas B.
• Application Number:
  US05/078,127
• Time in Patent Office: 652 Days
• Field of Search: 340/410,214
• US Class Current: 340/515
• CPC Class Codes: G08B 29/145 of fire detection circuits

Abstract

A fire alarm system including a plurality of fire alarms arranged in groups. Alarm-simulating conditions are produced in each fire alarm by an electric test signal, the response of each fire alarm being sent to an evaluation device at a central signal station through a circuit coupling the fire alarms together. Each alarm generates an oscillation in normal condition which is suppressed in the alarm state.

Claims

1. A fire alarm system comprising:

a plurality of fire alarms connected in parallel together in at least one group;

a central signal station;

conductor means connecting said central signal station with said plurality of fire alarms, the number of said conductors being independent of the number of said fire alarms of each group;

means for generating an electric test signal during an alarm checking operation;

said fire alarms including means responsive to said electric test signal to cause each of said fire alarms which are in a functionally ready state for detecting a fire condition to respond the same as if an actual fire alarm condition were present;

electrical circuit means for said plurality of fire alarms for producing no alarm-checking response signals when all fire alarms of a group have responded to said electric test signal and producing an alarm-checking response signal when at least one fire alarm of a group has not responded to said electric test signal; and

means for sensing at least one of said respective response signals.

2. A fire alarm system comprising:

a plurality of fire alarms connected in parallel together in at least one group;

a central signal station;

conductor means connecting said central signal station with said plurality of fire alarms, the number of said conductors being independent of the number of said fire alarms of each group;

means for generating an electric test signal during an alarm checking operation;

said fire alarms including means responsive to said electric test signal to cause each of said fire alarms which are in a functionally ready state for detecting a fire condition to respond the same as if an actual fire alarm condition were present;

an electrical circuit means for said plurality of fire alarms for producing no alarm-checking response signals when all fire alarms of a group have responded to said electric test signal and producing an alarm-checking response signal when at least one fire alarm of a group has not responded to said electric test signal, each fire alarm includes an oscillator means, the oscillations of which are suppressed when each said fire alarm is in its fire alarm condition; and

means for sensing at least one of said respective response signals.

3. A fire alarm system as claimed in claim 2, wherein said conductor means comprises two power supply conductors coNnected to each fire alarm, said oscillator means of each fire alarm being connected together by one of said power supply conductors, a transformer having a primary winding and a secondary winding electrically connected with said electrical circuit means, said primary winding being connected to said one of said power supply conductors, and said secondary winding providing the input of said means for sensing said response signals.

4. A fire alarm system as claimed in claim 3, wherein said oscillator means comprises a saw-tooth generator.

5. A fire alarm system as claimed in claim 4, wherein said two power supply conductors comprise a positive conductor and a negative conductor.

6. A fire alarm system as claimed in claim 5, wherein said saw-tooth generator includes a glow-discharge tube having an anode and a cathode, said cathode being connected to said negative conductor;

a capacitor and a resistance means connected in parallel with said capacitor, one terminal of said capacitor being connected with said positive conductor, the other terminal of said capacitor being connected to said anode of said glow-discharge tube.

7. A fire alarm system as claimed in claim 6, wherein said resistance means comprises a first and a second resistor connected in series;

each said fire alarm further comprising a cold-cathode tube having an anode, a cathode and a starter electrode, said anode electrode being connected to the junction point of said first and second resistors, said cathode electrode being connected to said negative conductor;

a third resistor;

each of said fire alarms comprising a measuring ionization chamber and a reference ionization chamber connected in series between said junction point of said first and second resistors, and said third resistor;

said third resistor being connected to said negative conductor; and

means connecting said starter electrode of said cold-cathode tube to the junction point between the measuring ionization chamber and the reference ionization chamber.

8. A fire alarm system as claimed in claim 7,each of said fire alarms further including a second capacitor connected to said positive conductor at one terminal thereof and connected to said third resistor at the other terminal thereof;

a diode connected in parallel with said third resistor; and

wherein said electric test signal comprises a reduction in potential of said positive conductor.