Photoelectric smoke detectors are placed in critical areas to detect a fire early enough so the entire family can be alerted to get to safety. 

The detector also communicates with the CPU for relaying of the alarm signal to the fire department.

Rate-Of-Rise heat detectors are used in areas of the house where, if a fire develops, it may not be smokey, but there will likely be flame, and a rapidly rising air temperature.  Locations such as the garage, furnace room, and laundry room are appropriate places.  Like the smoke detector, it's about five inches in diameter.

It's very important that the system make noise, and the really important place that it makes the noise is inside the house.  It will tell the burglar he tripped an alarm, and his desire for stealth will quickly drive him away.

Outside noise makers serve no useful purpose, except to annoy your neighbors during an accidental alarm.

One of the most important parts of any system is the passive deterrent protection provided by the alarm company sign and decals on doors and windows. 

It's too easy to simply go to another house that has no alarm.

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