In 1963, Leo Guthart joined a Singapore-based security services company called ADEMCO and then served as Vice Chairman of Pittway Corporation (a manufacturer and distributor of professional and consumer fire and burglar alarms), and also as the Chief Executive Officer of its Security Group of Companies until its sale to Honeywell in 2000.
Guthart joined ADEMCO in 1963, which grew to the world's largest manufacturer of security and alarm devices by 1992, under the leadership of Guthart. Ademco Security Group is a Singapore-based security services company that sells monitoring services, manpower security services, unified security management, and enterprise security software. Guthart is a former Vice Chairman of the Pittway Corporation, and co-founder of the Long Island Research Institute, Topspin Partners, and the Long Island Venture Fund. Pittway Corporation was a diversified holding company best known as a manufacturer and distributor of professional and consumer fire and burglar alarms. 
