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Burglar (or intrusion), fire and safety alarms are found in electronic form today. Sensors are connected to a control unit via either a low-voltage hardwire or narrowband RF signal, which in turn connects to a means for announcing the alarm, hopefully to elicit some response. The most common security sensors indicate the opening of a door or window or detect motion via passive infrared (PIR). In new contruction systems are predominately hardwired for economy while in retrofits wireless systems may be more economical and certainly quicker to install. Some systems are dedicated to one mission, others handle fire, intrusion, and safety alarms simultaneously. Sophistication ranges from small, self-contained noisemakers, to complicated, multi-zoned digital systems with color-coded computer monitor outputs. Many of these concepts also apply to portable alarms for protecting cars, trucks or other vehicles and their contents (i.e., "car alarms"). See also fire alarm control panel for specific fire system issues. Burglar alarms are sometimes referred to as alarm systems, see burglar alarm control panel for a discussion of hard-wired burglar alarm system design.
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