RE: Big Brother house (on topic I promise) and electronic door locks

["James Hoye" <james.hoye@xxxxxxx>]

This email was delivered t  you by The Free Internet,
a Business Online Group company. http://www.thefreeinternet.net
---------------------------------------------------------------
> One thing t  consider is the fire safety aspects.  If a fire causes an
> alarm to be triggered either intentionally or otherwise, the doors
will
> lock blocking your escape route.
> For this reason it is best to make the internal doors the unlock
> on failure
> types, that way if you can kill the power the doors will unlock.
>
> This raises the question of what you do for external doors though.
> Obviously if you have a power cut you don't want the doors to open but
at
> the same time you don't want to be locked out.

There are two modes of operation - fail release and fail secure.  As Steve
pointed out, you would want a fail release mechanism on internal doors. 
The
external door would need some sort of override mechanism - if using a fail
secure door strike with a cylinder operated rim latch
http://www.screwfix.com/product.phtml?2146,
then you could turn the knob to
get out (unless it was deadlocked in which case you would need the key as
well).

The magnetic locks employed in access control systems in many new offices
operate on a fail release principle.  They use a small energising current
to
keep the door locked, and for authorised entry this current is momentarily
removed.  They are battery backed up which can keep the lock energised
during a power failure, and the break glass will cut this energising
current
allowing the lock to release.  Of course, if there's a 26 hour power cut,
the battery may well run flat, thus releasing the door (not useful if you
are on holiday at the time!).

James H




____________________________________
Automated Home UK
http://www.automatedhome.co.uk
____________________________________

Your use of Yahoo! Groups is subject t  http://docs.yahoo.com/info/terms/