Voice alarm systems used for evacuation

[Sherpa]

The regulations state that two seperate circuits should be interleaved, and both circuits should be present in all areas of the building. Does this mean that even small offices should have speakers from two seperate circuits?

[Big_Fella]

Its the same as the old 'sounder rule' with interleaving, and that didnt require two sounders within a room.

The BS for voice alarm systems states that the circuits should be interleaved.  Not to the point of 2 speakers in a small office on two different circuits.

It states interleaved and also states that should a circuit fail some areas will still have annunciation, but maybe at a reduced Rasti level (eg. circuit in the room failing, but circuit in the corridor outside the room maybe functional and a speaker can be heard but at a reduced volume).

[Sherpa]

Thanks for that, it makes a lot of sense.

Tell me how does the intelligibility get determined these days, there seems to be a shift away from RASTI testing.