I don't think there are any security companies on the 900 Motorola system. It is getting close to empty. I have heard rumours that Nextel bought it and will be shutting it down soon, so that they can use the 900 freqs for IDEN during the 800 rebanding process. The only real use on the system is from one or two garbage companies, Pizza Caboose, Thrifty Car Rental, Titan Freight, Romar Trucking and a few other businesses. I havent listened to it much in a few months so some of them might be gone as well?