Simplex 4903-9418 Category : Simplex The lack of TrueAlert branding on the front of the alarm, as well as the odd grille, are signs that this is an early version of the TrueAlert. Brand SimplexModel 4903-9481Manufacturer SimplexType Alarm (Speaker/Strobe, 4-Wire)
Wheelock MT-24-LSM Category : WheelockI believe that this MT is newer than the Wheelock MT4-24LSM, yet older than the Wheelock MT-24MCW.
System Sensor 5603 Category : System SensorAll of the writing and printing on the exterior of the detector takes away from its overall appearance.
