Smoke detecting apparatus with multiple detectors connected to coincidence circuit

Claim 2

A smoke detecting system, comprising a plurality of smoke detectors of the ionisation chamber type having respective outputs at which are produced electrical warning signals in the presence of smoke, coincidence means having the same number of inputs as the number of said detectors, the said inputs being respectively connected to the outputs of the detectors, the coincidence means having an output at which is produced an output signal only when the plurality of its inputs simultaneously receive said warning signals, and output means connected to the output of the coincidence means to produce an alarm indication in response to the said output signal.

Claim 3

A system according to claim 1, including a second plurality of smoke detectors of the ionisation chamber type having respective outputs at which are produced electrical warning signals in the presence of smoke, second coincidence means having the same number of inputs as the number of detectors in the said second plurality, the inputs of the second coincidence means being respectively connected to the outputs of the detectors of the second plurality, the second coincidence means having an output at which is produced an output signal only when the plurality of its inputs simultaneously receive said warning signals, and output signal connecting means connecting the output of the second coincidence means to the said output means in parallel with the output of the other said coincidence means to produce a said alarm indication in response to either said output signal.

Claim 4

A system according to claim 2, in which the said output signal connecting means comprises an OR gate.

Claim 5

In a smoke detecting system, comprising a plurality of ionisation smoke detectors physically distributed about an area to be protected, each detector of which plurality includes a chamber to which the atmosphere in which smoke is to be detected has ingress and having two polarised electrode means, means for ionising the atmosphere in the chamber, and means responsive to a change in the ionisation current between the electrode means to produce at a detector output a warning signal indicative of the presence of smoke in the chamber, the improvement comprising at least two coincidence means each having a plurality of inputs and a single output, means connecting the said outputs of a first group of the said detectors to the inputs of one said coincidence means whereby the coincidence means produces an output signal at its said output only when all its said inputs simultaneously receive said warning signals, means connecting the said outputs of a second group of the said detectors to the inputs of the other said coincidence means, the second group of detectors including at least one detector from the first group thereof, whereby the said other coincidence means produces an output signal at its said output only when all of its said inputs simultaneously receive said warning signals, and output means connected to the outputs of both the coincidence means to produce an alarm indication in response to either said output signal.

Claim 6

In a smoke detecting system, comprising a plurality of ionisation smoke detectors physically distributed about an area to be protected, each detector of which plurality includes a chamber to which the atmosphere in which smoke is to be detected has ingress and having two polarised electrode means, means for ionising the atmosphere in the chamber, and means responsive to a change in the ionisation current between the electrode means to produce at a detector output a warning signal indicative of the presence of smoke in the chamber, the improvement comprising at least two coincidence means each having a plurality of inputs and a single output, means connecting the said outputs of a first group of the said detectors to the inputs of one said coincidence means whereby the coincidence means produces an output signal at its said output only when all its said inputs simultaneously receive said warning signals, means connecting the said outputs of a second group of the said detectors to the inputs of the other said coincidence means, the second group of detectors including at least one detector from the first group thereof, whereby the said other coincidence means produces an output signal at its said output only when all of its said inputs simultaneously receive said warning signals, and output means connected to the outputs of both the coincidence means to produce an alarm indication in response to either said output signal.

Claim 7

A smoke detecting system, comprising first and second pluralities of smoke detectors of the ionization chamber type having respective outputs at which are produced respective electrical warning signals in the presence of smoke, first and second coincidence means each having the same number of inputs as the number of said detectors in the first and second pluralities of detectors respectively, the inputs of the first coincidence means being respectively connected to the outputs of the detectors of the first plurality and the inputs of the second coincidence means being respectively connected to the outputs of the detectors of the second plurality, each coincidence means having an output at which is produced an output signal only when the plurality of its inputs simultaneously receive said warning signals, third coincidence means having two inputs and an output, means connecting the said output of one of the detectors of the first plurality thereof to one of the inputs of the third coincidence means in parallel with the input of the first coincidence means to which that output is also connected, means connecting the said output of one of the detectors of the second plurality thereof to the other input of the third coincidence means in parallel with the input of the second coincidence means to which that output is also connected, the third coincidence means producing an output signal at its said output only when both of its said inputs simultaneously receive said warning signals, output means for producing an alarm indication in response to the said output signal, and output signal connecting means connecting the outputs of the first, second and third coincidence means to the said output means in parallel so that the said output means produces an alarm indication in response to any one of the said output signals.

Claim 8

A smoke detecting system, comprising first and second pluralities of smoke detectors of the ionization chamber type having respective outputs at which are produced respective electrical warning signals in the presence of smoke, first and second coincidence means each having the same number of inputs as the number of said detectors in the first and second pluralities of detectors respectively, the inputs of the first coincidence means being respectively connected to the outputs of the detectors of the first plurality and the inputs of the second coincidence means being respectively connected to the outputs of the detectors of the second plurality, each coincidence means having an output at which is produced an output signal only when the plurality of its inputs simultaneously receive said warning signals, third coincidence means having two inputs and an output, means connecting the said output of one of the detectors of the first plurality thereof to one of the inputs of the third coincidence means in parallel with the input of the first coincidence means to which that output is also connected, means connecting the said output of one of the detectors of the second plurality thereof to the other input of the third coincidence means in parallel with the input of the second coincidence means to which that output is also connected, the third coincidence means producing an output signal at its said output only when both of its said inputs simultaneously receive said warning signals, output means for producing an alarm indication in response to the said output signal, and output signal connecting means connecting the outputs of the first, second and third coincidence means to the said output means in parallel so that the said output means produces an alarm indication in response to any one of the said output signals.

Claim 9

A system according to claim 5, in which the said output signal connecting means comprises an OR gate.