[Cialug] OT: Alarm systems

[Nathan C. Smith]

Anyone familiar with household alarm systems?  (I know at least one person is)

In houses that are wired or pre-wired for Alarms, the smoke detectors are often wired too.  Are they wired just for power or are they wired with signal cable to so that they can connect to the alarm system as well?  Mine seem to be wired for power but I haven't taken a multimeter too them yet.

Further, would a signal cable be an on-off type of thing or would there actually some kind of coded digital or analog signal on the smoke detectors?  I suppose it could depend on the brand and price of the smoke detectors?

-Nate