Writer needs info on burglar alarms

["Tim Walters" <tim.walters@xxxxxxxxxxx>]

I'm writing a story set in 1988. One of the characters has to break into
someone's house. He's not a burglar, but a professional architect who's kept
abreast of the latest developments in household security. The alarm he has
to disarm is up-to-date at that time. But he needs not only to deactivate
the alarm, but also to conceal the fact that it's been disarmed.

If it's an infrared heat detector with a four-digit disarming code, it would
also be helpful if, after disarming the device once, he could now work out
what that code was so as to break in again more easily later on.

Thanks in advance for any help.

Tim
(For e-mail s u b r u b)