Danger alarm system

Claim 1

A danger alarm system comprising: a plurality of call lines for calling signals; a plurality of alarm circuits connected to respective call lines and operable to provide environment condition signals to said lines; and a central exchange connected to said call lines, said central exchange including a plurality of alarm connection circuits connected to respective call lines and each having three outputs and each operable to provide signals including alarm and line interrupt signals in response to the environmental signals, a write-read memory including a plurality of storage locations each including an input and an output and each assigned to store the busy or non-busy state of a respective line, a plurality of synchronously operable multiplexers, first and second ones of said multiplexers connected to read said first and second outputs, respectively, of said plurality of alarm connection circuits, a third one of said mulitiplexers connected as an interrogation multiplexer to said outputs of said memory, a comparison circuit connected between said third, interrogation multiplexer and said first and second multiplexers and operable to compare alarm and interrupt signals with the busy status of the respective call lines and responsive to a busy state in conjunction with an alarm signal to produce an alarm output signal and responsive to a busy state in conjunction with an interrupt signal to produce an interrupt output signal, alarm evaluation circuits operable in response to alarm output signals, interrupt evaluation circuits operable in response to interrupt output signals, a fourth multiplexer connected as an alarm multiplexer between said comparison circuit and said alarm evaluation circuits, and a fifth multiplexer connected as an interrupt multiplexer between said comparison circuit and said interrupt evaluation circuits.