Abstract: An occupancy simulator for casting shadows on the walls of a room, the simulator having a lamp, a shutter for casting the shadow by passing through the lamp's light beam, a motor for driving the shutter, and a microprocessor for controlling the operation of both shutter and lamp so that the shadow moves first in one direction and then, after a delay, in the reverse direction in its base mode of operation. The microprocessor can be programmed to start and stop the base mode, to modify the base mode and to cycle through the base mode in response to an external signal such as from a home security system. Several occupancy simulators can be electrically tied into a supervising unit of a home security system to cycle one or more occupancy simulators in sequence through the base mode upon receiving a signal that one of the detectors of the home security system has been tripped.