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BS7273-4 compliant interface to fire alarm panel


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Hi, I'm hoping someone can help me deciding the best way to interface a device to a fire alarm for Critical Category BS7273-4 compliance. I'm trying to decide which is the most common interface type that is generally available on fire alarm panels without having to use volt-free relays or anything that might 'steal' valuable resources from the fire alarm panel for a dedicated interface.

According to BS7273-4 diagram C1.b, I'd need an output from the alarm that is passes in series through a normally closed fire relay and normally closed fault relay (at least one being normally energised) and a power supply in series with this too. I assume the AUX 24V supply could be used for this supply which I also assume is short circuit protected (?). That would normally provide a 24V signal that is removed on either a fire or fault condition, and would provide fail-safe short and open circuit protection on the two wire interface to my device.

1) Are my assumptions above correct?

2) If so, do fire alarm panels provide these as single outputs that effectively do the above? Are they called auxilliary outputs?

3) Can such a output be used to trigger multiple devices?

The BS7273-4 spec does show a single 'auxilliary output' (figure C4) triggering a radio TX device, I assume the ground return isn't shown but to make this Category A compliant it would I think need to use the same methodology as above, namely fail-safe and triggering by fault or fire.






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