×

Alerting process and system of apparatus therefor

  • US 4,031,467 A
  • Filed: 09/19/1975
  • Issued: 06/21/1977
  • Est. Priority Date: 09/19/1975
  • Status: Expired due to Term
First Claim
Patent Images

1. A localized area warning system comprising, in a large geographically defined area, a radio frequency transmitter provided with (a) means for producing a plurality of modulating signals each of fixed frequency in range of 20 to 3,000 Hz, and (b) means for producing a fixed radio frequency output, and, in each of several separate smaller geographically defined area portions within said one large area, a plurality of radio frequency receiving circuits each comprising an audio frequency detector assembly with an electrical output and a power input operatively connected thereto, said output of said detector assembly connected to a loud speaker through a normally open first switch operatively connected to a first switch closing means therefor, said first switch closing means connected to means providing an input signal to a time delay means, said time delay means having an output operatively connected to a circuit controlling said first switch closing means whereby to close said first switch at the end of a predetermined time period,an audio frequency signal receiving circuit operatively connected to the output of said audio frequency detector assembly and selectively actuated only by one audio frequency signal characteristic of one smaller geographical area portion;

  • an electrical power source operatively connected to said audio frequency receiving circuit,a second time delay circuit having an input operatively connected to and actuated by said audio frequency signal receiving circuit and having an output operatively connected to a second switch closing means between a power source for said first switch closing means and said first switch closing means whereby to provide a predetermined time of connection of said loudspeaker to said audio frequency detector assembly on receipt by said audio frequency receiving circuit and said audio frequency detector assembly of said one audio frequency signal for a predetermined time period, anda volume control means connected between said radio frequency receiving circuit and said loudspeaker,a third normally open switch controlled by a relay therefor and said third switch bridging said volume control means when closed,said relay operatively connected to and maintained in operative connection to a power source by said first time delay means and said relay when actuated closing said third switch, and wherein each of said audio frequency signal receiving circuits is located in a casing that carries identification of said separate smaller geographically defined area in which to be used.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×