hensoa
they are 2 detectors however as you note you can use the vibro side in lathing mode so that you can have more than 1 per circuit. It is better to have 1 device per circuit but obvioulsy this does increase the cost.
28 zones is not uncommon but a lot of people (non approved installers etc) just pt a lad of detectors on 1 circuit to lower the cost. This is obviously not ideal.
Yes they can be in any dry location, however id be extremely cautious about usiong vibration detectors on a shed, ie wind, rain, hail etc.
They do an rf keyfob if thats what you mean but you would need a wireless expander for the premier to accept these.
There are no external keypads, however as long as the location is dry it will be fine.
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