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Abstract

A central protection system suitable for the protection of a building from fire and other hazards includes a set of environmental sensors and circuitry for interrogating the sensors. The system also includes communication and control lines, as well as monitoring circuitry having individual channels coupled to respective ones of the communication and control lines. An inaudible pilot tone of subsonic frequency may be coupled to a communication line, and the corresponding channel of the monitoring circuit includes a detector of the pilot tone. A circuit for the generation of evacuation signals and fire brigade signals is composed of two sections coupled in tandem, and includes sequencing circuitry for the recycling of tones produced by the respective sections.

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First Claim