Yarnell Security Systems, 31 E South St, York, PA 17401, US

ADT Security Services has been a leader in home and commercial security services since 1874. The company, which was acquired by Tyco International in 1998, has more than 1 million customers in 230-plus markets throughout the United States. For home security, ADT has systems that monitor carbon monoxide levels, smoke and fire detectors, burglary alarms, low temperature sensors, water/flood sensors and a safewatch cellguard system in place to keep security systems operating if regular residential phone service is out. Small business security services include video surveillance, intrusion detection and online customer service. ADT Security Services also has products available for large businesses and government institutions. The company has locations spread throughout the U.S., including one in Fort Washington, Pa. ADT is headquartered in Lancaster, Pa.