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System for transmitting alarm information over telephone lines

  • US 4,262,283 A
  • Filed: 03/01/1978
  • Issued: 04/14/1981
  • Est. Priority Date: 03/04/1977
  • Status: Expired due to Term
First Claim
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1. An alarm system for transmitting alarm information to desired terminal stations via telephone lines comprising:

  • a plurality of transmitters which are located at telephone subscribers'"'"' premises, each transmitter having an alarm circuit associated therewith and being adapted to transmit signals indicative of the state of its associated alarm circuit to a telephone line, said signals being in the form of modulated carrier waves,a respectively corresponding plurality of receivers located at one or more local telephone exchanges, each receiver being associated with a respectively corresponding transmitter for receiving the transmitted signals therefrom,the or each local exchange having a local processor which is arranged to sequentially scan the outputs of the receivers located at its exchange and, when it detects a signal indicative of an alarm condition, to transmit a signal coded with information indicative of subscriber identity and of the desired terminal station to which the alarm information is to be routed, anda central processor including a store for storing alarm information which allows the alarm information to be redirected from one terminal station to another, which central processor is connected to receive such coded signals transmitted from said local processor and to direct the alarm information to a desired one of a number of said terminal stations, wherein each said transmitter is arranged to produce a carrier wave which is modulated with one or more of a plurality of other frequencies according to the state of the alarm being monitored.

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