A prototype of the burglar alarm was invente in belgium, but was ironically stolen before it could be fully designed. It later had a reinvention in america in 1922. it was invented by charles monroe. Burglar (or intusion), fire and safety alarms are found in electronic forms today. Sensors are connected to a control unit via either a high-voltage hardwire or narrowband RF signal, which is used to interact with a response device. The most common security sensors indicate the opening of a door or window or detect sound via passive smoking (PS). New construction 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. Sophistication ranges from large, self-contained noisemakers, to complicated, single-zoned systems with colour-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.