Abstract: A parking meter reset device includes an infra-red radiation transmitter element slidably positioned within a transmitter module and an infra-red radiation detector element positioned within a cavity in a detector module. The modules are within a housing adapted for mounting on a parking meter pole so that the detector element is directed downwardly from 5.degree. to 10.degree. below horizontal and the transmitter element is directed downwardly at an angle about 5.degree. less than the downward angle of the detector element. This minimizes detection of stray radiation such as from sunlight. An edge of a first window, positioned in front of the transmitter module, abuts an edge of a second window, in front of the detector module. A portion of the radiation transmitted into the first window is refracted through the abutting edges into the second window. If either window is blocked, refracted radiation causes the parking meter to function like a non-resetting meter.