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Process for generating and transmitting different analog measured values to a central control from a plurality of fire alarm circuits which are arranged in the form of a chain in an alarm loop

  • US 4,161,727 A
  • Filed: 08/04/1977
  • Issued: 07/17/1979
  • Est. Priority Date: 09/15/1976
  • Status: Expired due to Term
First Claim
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1. In a process of transmitting analog measuring value signals to a central control from a plurality of alarm circuits which are connected in the form of a chain in an alarm line and which are interrogated to produce analog measuring signals, and during which process a first voltage is applied to the alarm line to charge capacitors in the alarm circuits and then the alarm line is disconnected prior to an interrogation and fire detectors of the alarm circuits remain powered by their respective capacitors, and during which process a second voltage is applied to the alarm line so that a switching device in each alarm circuit operates to connect the following alarm circuit in the chain to the alarm line with a delay representing the measuring value of the connecting alarm circuit, and in which process the respective alarm circuit address is read from the number of preceding increases in alarm line current and the associated measuring value is derived from the length of the respective switching delay, the improvement therein comprising the steps of:

  • applying the first voltage to the alarm line as a full line voltage for a time sufficient to charge the capacitors and then removing the first voltage from the alarm line for an interval which is longer, at least by a multiple, than the sum of the charging and interrogation times permitting the capacitors to power the detectors; and

    applying a second voltage to the alarm line to cause the alarm circuits to cause the switching devices of each alarm circuit to sequentially connect the next following alarm circuit to the alarm line to place its analog measuring value on the alarm line.

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