Although Ademco might not be as popular of a name when it comes to alarms as security companies such as ADT, Ademco actually is important to the success of the ADT. Ademco manufactures many of the security systems that ADT sells and monitors. If an Ademco alarm sounds on accident, you will likely want to reset it as soon as possible. Resetting the alarm takes only a moment, but you must know the alarm's code, which you received when the installer hooked up the system.