Abstract: Each of plural detection units performs a signal transmission-reception operation responding to at least one of a plurality of kinds of operation timing signals repeated at a predetermined periodicity. The number of continuous reception times of the reflection signal is counted and used to determine obstacle detection when the number of counts is larger than or equal to a predetermined value. The transmission-reception operations are controlled by an operation timing signal having a periodicity shorter than the predetermined periodicity.

Abstract: An obstacle detection device has detection units, each of which performs a signal transmission-reception operation for sending detection signal to a detection area allotted thereto and receiving reflection signal from the detection area, an operation control unit for controlling the detection unit so that the detection unit performs the signal transmission-reception operation responding to at least one of a plurality of kinds of operation timing signals repeated at a predetermined periodicity, and a determination unit which counts a number of continuous reception times of the reflection signal of the detection unit and determines an obstacle detection in the detection area when the number of the continuous reception times thereof is larger than or equal to a predetermined value.

Abstract: In a load actuation circuit of an emitter-follower circuit arrangement, a surge detection circuit detects a power surge voltage superposed on a power voltage of a power line. A feed circuit supplies current to a control electrode of an output transistor (i.e. emitter-follower transistor) from the power line to turn on the output transistor forcibly when any power surge voltage is detected by the surge detection circuit. Thus, the power surge voltage is absorbed by the output transistor.