Re: Re: comfort fitting

["Frank Mc Alinden" <armagh@xxxxxxx>]

Hi David

> The traditional method for UK wired alarms is to have two loops to
> each contact assembly (or PIR or whatever),

This method was also used here in Australia until the introduction of dual
EOL,S........


> The Americans achieve the same result, but do it dfferently; they use
> an end of line (EOL) resistor across the cntact, so that even hen the
> contact is open, there is a measurable resistance.  Trouble is,this
> method doesnt detect shorts on the wire, so by using a second
> resistor in series with the cotact you can detect the four states
> needed, namely open circuit, short circuit, contact open, contact
> closed.

The traditional method also used (here in aussie) an EOL resistor and so
long as you put the resistor at the sensor eg pir (End Of Line) then the
alarm panel will detect a short along the signal wires .
As for the dual EOL,s as far as i know it  main purpose is to allow
detector status and tamper status on one pair of wires ..there by saving on
using 4 core instead of 6 core........

I have done some installs for a guy who designed his own stuff and he
used 3 resistors............

Frank


----- Original Message -----
From: "the_home_automator" <db@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Wednesday, March 05, 2003 10:17 AM
Subject: [ukha_d] Re: comfort fitting


> --- In ukha_d@xxxxxxx, "Frank Mc Alinden"
<armagh@b...> wrote:
> > Hi Des
> >
> > > Whats a 24 hr loop for?
> > >
> >
> > This is used for Panic buttons (hold up situation) equipment
> tampers.. eg
> > bell box ..industrial alarms.....fire doors (which normally kept
> closed)
> > etc...
>
> And just for completion here - your insurance company definition of
> an alarm system will be "it complies with BS4737", and one
of the
> specfic requirements in this standard is tamper protection for all
> items of the entre system.
>
> The traditional method for UK wired alarms is to have two loops to
> each contact assembly (or PIR or whatever), one of which is armed
> 24x7 so if the wirnig is interfered with it is detected.  Thats why
> UK alarms use four core security cable, or six core for things that
> need 12v, like a PIR.
>
> The Americans achieve the same result, but do it dfferently; they use
> an end of line (EOL) resistor across the cntact, so that even hen the
> contact is open, there is a measurable resistance.  Trouble is,this
> method doesnt detect shorts on the wire, so by using a second
> resistor in series with the cotact you can detect the four states
> needed, namely open circuit, short circuit, contact open, contact
> closed.
>
> UK fire alarm practice universally use end of line resistors, its
> just intruder alarms that are diferent.
>
> David.
>
>
>
> http://www.automatedhome.co.uk
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