Cutting and extending alarm cable problem

They have a re-chargeable battery inside them which is charged by the main panel power supply.

Two of the wires form an anti-tamper (24hr) circuit. Depending on how sophisticated your system is, shorting those should stop it sounding when the wire is cut. But you'd need to know which colours were used for this. Which would mean opening up the main panel. You'd need the installation instructions for that to know how to prevent it reacting to being tampered with.

Turn the alarm off before you do it, FFS!

MBQ

Sorry, that should be turn the alarm off so you can open the bell box without it sounding and disconnect the battery.

MBQ

Turning the alarm off may not work, if you read that to mean disconnecting it from the mains. However, assuming you have the instruction book to tell you how, enter into "Engineer" mode, this normally disables the tamper circuit, otherwise when you open the alarm box to disconnect the battery the alarm will be activated.

If you had read the OP correctly, you would have learned that the battery was disconnected and that the sounder was getting power from a capacitor. The capacitor is there to provide power if some one cuts the wires or otherwise tampers with the system. Tell you what,come round and put your fingers on the contacts of the capacitor and you soon learn what it does.

On Fri, 5 Jun 2009 03:13:37 -0700 (PDT) someone who may be Vet Tech wrote this:-

It must be quite a capacitor if it powers the sounder for an hour.

Err, I doubt it. Unlikely to be more than a couple of volts.

You can get such things - but all the bell boxes I've seen use an ordinary re-chargeable battery.

unset) and cannot be defeated. The only way to do it is remove the sounder from the wall, the sounder will sound as it has an anti-tamper switch, then disocnnect it's battery, then extend the cable and put the sounder back on.

Your alarm panel itself will HAVE to be in engineer mode to do this, otherwise the internal sounder will sound too.

-K

"Vet Tech" wrote

To clarify the other posters' comments hopefully....

The bell box has an internal battery which (as you have discovered) will sound if the wire to it is cut. If you have a sufficiently sophisticated alarm system/bell box there may be a procedure to enable a form of engineer/access mode for the bell box itself. This allows the bell box lid to be lifted without activating the tamper switch and then you can disconnect the internal battery. After that you will need the alarm panel engineers' code to allow access to the panel to power it down and remove internal backup battery.

If your bell box isn't the smart type, then you will have to do the bellbox battery disconnect "live" (with earplugs).

So.. Remove mains supply to panel - usually remove fuse from spur. If your internal panel backup battery is shot, then the bell box will sound at this point. This is because the bell box requires a hold-off supply from the panel which is lost when all power to the panel drops. (This is why loads of alarms sound whenever there's a power cut - indicates spent panel battery). Enter engineers' code for panel access and to defeat the panel lid anti-tamper circuit (this will not defeat the bell box anti-tamper). Check out the details for your bell box if you can find them. As supplied, they usually have a "not connected" terminal for the supply from the bell box battery to the internal ciruitry. With earplugs fitted, remove bell box lid and disconnect internal bell box battery, moving wire from existing terminal to "not connected" terminal. Open alarm panel (with mains feed off - check) and disconnect internal panel battery. Noise should now cease, and disconnect of bell box cable should be possible.

HTH

Phil

prevents me

but it's only 20 mins! Most are 12v systems and use a gel cell rechargeable in the alarm sounder box which will also have a tamper switch on the case. I'd doubt it's a capacitor rather than a battery, but it is technically possible nowadays, as capacitors of several farads are available at low voltages. When I was a boy I can remember the physics teacher saying that the farad unit was impractically large 'as you'll never see a one farad capacitor' - well I have several 3.3 farad capacitors !

AWEM

"Dave Plowman (News)"wrote

Most modern bell boxes need a hold-off supply to stop them sounding. This is why bell boxes sound when there's a power cut (internal panel battery not replaced regularly....therefore loss of mains = total loss of power to panel = loss of hold-off signal).

Phil

On Fri, 05 Jun 2009 11:26:12 +0100 someone who may be "Dave Plowman (News)" wrote this:-

That was certainly the case when I was involved with such things too.

Which won't stop it sounding!

I would not like to touch the stobe light connections when stood at the top of a ladder!

The capacitor on it's own would not bother me.

Adam

The trigger pulse is usually something like 1kV-4kV, but it's extremely short and low energy. I have accidentally touched one in another application, and I didn't notice at all, except that it stopped the flash tube firing.

However, you would get a belt off the flash capacitor, which is usually something like 200V-400V and contains the energy for one flash.

The other place you might get a belt is a peizo sounder, which is driven through a step-up transformer, but if you're that close when it's going off, deafness is more likely to be a concern.

Battery? Usually 3-4 NiCds.

Not sure many alarms have any concept of being turned off.

With mine, putting it into Engineer Test Mode allows you to remove the external sounder cover without it going off, but you must keep it connected to the panel whilst you do this. Once you have the cover off, you can remove the internal battery jumper, and then disconnect the wiring.

The strobe will be very low current and unlikely to actually hurt.

On the alarm boxes I've seen, the anti-tamper is done by feeding a constant 12v to the bello box. If that supply drops, the battery kicks in and sounds the alarm.

If it's like that, you need to arrange a 12v supply to connect the correct wires to when you cut the cable.