FIRE ALARMING SYSTEM

• US 3,753,258 A
• Filed: 03/10/1971
• Issued: 08/14/1973
• Est. Priority Date: 03/31/1970
• Status: Expired due to Term

• Current Assignee: Yukio Honda
• Original Assignee: Yukio Honda
• Inventors: Honda, Yukio
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Partridge, Scott F.
• Application Number:
  US05/122,956
• Time in Patent Office: 888 Days
• Field of Search: 340/227,228,191,179,181,408,182,185,224,171PF,184,413,416,171,237 310/8.1 343/6.5,6.5SS
• US Class Current: 340/524
• CPC Class Codes: G08B 17/11 using an ionisation chamber for detecting smoke or gas
• CPC Class Codes: G08B 25/04 using a single signalling line, e.g. in a closed loop

Abstract

A fire alarm system having a plurality of fire detectors connected in parallel to a transmission line, each detector having a band pass filter resonating at a specific individual frequency. A receiver is connected to the transmission line and generates a plurality of frequencies corresponding to the frequencies of the detectors and has means for detecting specific frequencies returned thereto when one or more of the detectors are activated by fire, thus enabling detection and location of a fire.

Claims

1. A fire alarm system comprising a plurality of fire sensing units connected in parallel between a pair of conductors, a receiving unit including a voltage source and an alarm device connected to said conductors, each of said fire sensing units including a normally open switch which is closed to short circuit said conductors and energize said alarm device when a fire is sensed, each fire sensing unit further including a band pass filter connected between said conductors and having a characteristic resonant frequency preselected peculiarly to said sensing unit, said receiving unit further including means for generating a range of AC signals having frequencies corresponding to said characteristic resonant frequencies of said filters in the respective sensing units, each of said filters being operated upon actuation of its associated sensing unit to produce its characteristic frequency, a conductor directly connecting the outputs of said filters in said sensing units to said receiving unit and means in said receiving unit and connected with the last said conductor for discriminating the frequencies of the received AC signals and indicating the specific detector activated by the presence of fire whereby each detector upon activation produces both a general alarm and an indicating signal to identify at the receiving unit the specific detector actuated.

2. A fire alarm system according to claim 1 wherein each of said filters is an electromechanical band pass filter and each of said detectors includes a sounding device driven by said electromechanical filter.

3. A fire alarm system according to claim 1 wherein said indicating means includes a plurality of electric lamps.

4. A fire alarm system according to claim 1 wherein each of said fire sensing units sense both ambient temperature and smoke.