From: lsg001@cck.coventry.ac.uk (Graham Wilson)
Subject: Re: Alarm systems
Organization: Legal Department - Coventry University
Distribution: uk
Date: Thu, 17 Dec 1992 22:01:12 GMT

In article <BzF0vL.Iwu@newcastle.ac.uk> S.A.McIntyre@durham.ac.uk writes:
>Graham's response was complete and very accurate, but as having recently purchased an
>alarm system, I have a few things to add...
>
>The communicator:  When you have a communicator installed, it is important to note that
>you are only allowed 3 false alarms in a six month period before the Police strike your
>house of their list of quick response homes.

** In some cases the police have been know to refuse to answer the 
   alarm system. However, in order to cover themselves against the possibility
   of a negligence action, in this particular circumstance,  they will still
   respond but only when a police car happens to be passing in the vacinity
   on some other business.

   In severe cases, where an auto dialler is fitted -(this telephones the 
   operator and plays a pre-recorded message containing the alarm police
   ID code and other information)- the police have demanded that the 
   unit be re-directed to another telephone number so that the calls are
   not eventually routed through to them.

>	If the alarm is triggered by a break-in, PIR disruption, and so on, then no audible
>or visible warning will be made for about 10 minutes, which gives the Police time to
>arrive to catch the theif in the act.  Not all alarms operate this way, but in my opinion,
>it is wise.

** Most forces specifically require the timer to be set at 5 minutes, usually 
   counted from the time when the control centre sends back the "received"
   confirmation signal to the control pannel. It is only by special 
   arrangement that the police will allow this time period to be shortened
   or lengthened.

>	Some alarms (mine included) allow a DURESS option.  This means that if someone
>follows you into your house, and orders you to turn off the alarm under duress, you can
>enter a special code which will phone the police but NOT sound off the alarm.  This could
>be wise in life-threatening situations.  Obviously, the duress option only works if you
>have a digital communicator installed.

** One alternative which is very inexpensive, easy to install in systems but
   little know is the intelligent panic button. This contains two buttons.
   If the first button is pressed the panic button immediately activates the
   system as normal.

   The second button is for use when you go to answer the door and you are
   not sure who is there. You press the second button on the panic device
   before you open the front door. The panic button then starts to count-down
   from a presetable, predetermined time - Usually 2 minutes. If you are happy
   with the caller you return and press the button on the panic button and the
   timer stops. However, if someone forces there way into the house, you need
   do nothing if you are unable to reach the panic button and press the 
   "immediate alarm" button. When the timer reaches zero it automatically 
   activates the alarm system.

>	If your phone line is cut then the bells go off.  British Telecom has introduced a
>method whereby such communicators can tell the difference between cutoffs in service (due
>to works or storm, etc) and a snipped line.  I can't remember the details, but it has to
>do with the line generating a tone the communicator listens for, rather than the line
>voltage or current.

** The system sends a signal to the digital communicator every so often. The 
   digital communicator responds by sending a code. If no code is returned 
   or an alteration to the parameters of the line is detected then the 
   system investigates further and tries to determine the cause of the 
   problem. This information is then passed on within 7 seconds to the 
   control centre.



>	Most alarm companies rent the modem/communicator, rather than sell it to you. 
>This is largely to cover their costs of operating the hardware on the other side to
>receive it.  You technically own it, but pay an annual rental for the use of it.  This
>could be in the area of 100 pounds per year.
>
** There are two current arrangments here. In the case of a large national
   or multi-national company such as Chubb, Modern Alarms or British 
   Telecom Securtiy etc they will own their own monitoring station. In this
   case, the company might rent the communicator to you and include within 
   this price the monitoring station cost. However, in the case of the 
   smaller alarm company they will have an arrangement with a monitoring
   centre. The alarm company will sell you the communicator. However, the
   householder will be responsible for paying the monitoring station fee
   themselves.



>PIR:  Pets can be a problem with PIR systems.  If you have a dog, most alarm fitters can
>adjust the sensor to avoid a certain level (say about 4 feet).  Keeping in mind that cats
>are not effected by gravity, this method will not take care of them.

** "Pet alley" systems cause considerable problems for insurance purposes.
   A burglar can crawl on their hands and knees underneith a pet alley.
   Therefore, most insurance companies will not provide discounts where
   an alarm operating on a pet alley system is in operation. Usually, unless
   very special circumstances apply, according to the British Standard for
   Alarm Systems (BS 4737) pet alleys should not be installed. NACOS 
   installers are bound by the British Standads and are therefore usually
   unwilling to install pet alleys in a system where a NACOS certificate
   is to be issued.


>	Forced air heating sysytems can cause a problem for PIR sensors.  Most clever
>installers have ways around this, but make sure that you point you that you have such a
>system.
>	Draughts can cause problems...we had a few false alarms because of a draughty
>front door.  
>
** All alarm companies claim that their particular PIRs (Passive Infra-Red
   sensors) are very realiable. However, this statement is often very 
   misleading. Most firms will say that they install PIRs which operate
   on the pulse-count system. There is, however, simulated pulse-count
   and real pulse-count. The more expensive PIRs are usually fitted with
   proper pulse count at either level 2, 3 or 5.

   In other words before the passive will activate it must detect 2, 3 or
   5 pulses from the PIR zones in a logical sequence before it will activate.
   5 pulse are not normally used, apart from places where severe 
   environmental interference is present. The problem with 5 is that by moving
   very, very slowly through the field of detection it is often possible
   to deceive the PIR. The 2 or 3 pulse count detectors will pick up a 
   moving human being but are not as good at screening out environmental 
   disturbance. For the sake of an additional 5 - 10 per passive it is 
   worth while specifically asking your installer to use true pulse-count
   detectors.

   
-- 
         *********************************************************
         *      Graham Wilson      *  lsg001@cck.coventry.ac.uk  *
         *     LL.B.  Law  III     *     Coventry  University    *
         *********************************************************