Abstract: An ultrasonic sensor detects the time of rise of the first of transmitted waves and also detects peak points Po appearing in the waveform of received waves to detect a waveform reference point where the time-base coordinate of a phantom envelope connecting these peak points Po is a minimum. The time T2 of rise of the first of the received waves is calculated by adding a predetermined period of offset time To to the time t2 of the waveform reference point of the received waves to calculate the elapsed time .DELTA.T from the time of rise of the first transmitted wave to the time of rise of the first received wave. The distance L to an object of measurement is calculated based on the result of calculation. The distance L to the object can be calculated alternatively based on the elapsed time .DELTA.T' from a waveform reference point of the transmitted waves to the waveform reference point of the received waves.

Abstract: An electric working apparatus includes a movable body which is driven by a movement mechanism, and the movable body is provided with a working mechanism such as an articulated robot. The movement mechanism, the working mechanism and etc. are driven by an electric power which is supplied through a power supply cord being extended from a cord reel mechanism fixed on a wall or floor within a working space of the movable body to be connected to the movable body. When the movable body moves in a manner that the movable body goes away from the cord reel mechanism, a tension detection switch is turned-off by a lever, a reel motor is turned-off, and clutch plates are released, and therefore, the power supply cord is wound from the cord reel mechanism by necessary length.