SAFETY SYSTEM OF CONSTRUCTION MACHINE

摘要

PURPOSE:To prevent a failure to detect a distance due to battery runout by modulating a reception signal according to the output of a phase shifter which gives a specific phase shift according to a signal indicating a specific discharge state which is detected by a discharge state detection circuit of a battery. CONSTITUTION:A transceiver 10 is mounted to the rear of a hydraulic shovel and a transponder 20 is mounted to the helmet of a worker. The transceiver 10 is provided with an operation circuit for measuring the distance to the transponder 20 and then sends the calculated distance to the controller of an operation stand. The transponder 20 is provided with a switching circuit 25a for selecting either a phase shifter 25, the output of the phase shifter 25, or that of an oscillation circuit 22 and then transmitting it to a mixing circuit 23, a discharge state detection circuit 29 etc. The detection circuit 29 is constituted by a comparator and generates a detection pulse L when the voltage of a battery 40 goes below a preset value. A communication control circuit 28 receives a pulse L from the detection circuit 29 and turns on or off the circuit 25a.