SOUND OPERATED START CIRCUIT

摘要

The invention is concerned with starting of electrical machines from a sound emitting device and is particularly concerned with safety circuits for the start of a coal getting machine on the sounding of a klaxon giving warning to mine workers underground that the machine is to be started and hence to keep clear. The signal from the klaxon is detected as to certain predetermined parameters including amplitude, frequency and the rate at which the klaxon is being operated since it would normally be controlled by a water driven pump. The signal is then fed to a discriminator circuit which then determines that these parameters are correct. Two such circuits are provided in parallel with each other and a signal to enable the machine to be started is only provided at an output terminal when the correct signal is found and detected by both circuits simultaneously.