You can try using a series resistor to limit current and clamping the
signal with an MOV, Transorb, Diode or other clamping device. This is in
effect protecting from ESD but even more severe. Digital I/O are easier to
protect than analog I/O but the big problem is giving a path for this high
power impulse to go. Perhaps a gas discharge or spark gap would also help
on the lines vulnerable.
Another system that people are playing these types of game with are the
slot machines. These now have to be protected from this type of attack by
design.


At 10:46 AM 11/12/97 GMT+2, you wrote:
>Hi All
>My PIC based alarm system have been blown up with a High Voltage
>zapper; those handheld units for shocking people/animals...
>Aparently this is a new craze among burgulars. Thy kill home alarms,
>car alarms and cct video with these zappers.
>
>Short of using screen cable for every sensor, is there other devices
>or goodies that can protect alarm systems from this assult????
>
>Regards
>Cassie
>
>
Larry G. Nelson Sr.
mailto:L.Nelson@ieee.org
http://www.ultranet.com/~nr