Abstract: An alarm system has an alarm unit that includes a siren, a stroboscopic light, and an address display. The alarm unit is located on a building so as to be visible from the building exterior. The address display is made up of one or more characters, arranged so as to make up the address of the building. The characters are formed by plural light emitting diodes. Switching circuitry activates the siren and the stroboscopic light, and switches the display to full brilliance. Reset circuitry deactivates the siren and the strobscopic light, and returns the display to a preactivation level of brilliance. A portable transmitter unit can be used to activate the alarm system. Interlock circuitry prevents the deactivation of the stroboscopic light and the address display before the siren is deactivated. The alarm system can be operated in one of two modes. The first mode has the siren operate continuously, and the second mode has the siren operate intermittently.