Multifunction acoustic device

摘要

A multifunction acoustic device has a rotor rotatably supported in a frame, a stator provided in the frame. A permanent magnet is provided on the rotor, a coil is provided for forming magnetic fluxes between the rotor and the stator. Voltage detecting means is provided for detecting a voltage generating at the coil. A voltage detected by the voltage detecting means in the operation of the acoustic device is compared with a reference voltage which corresponds to a voltage generating at abnormal rotation of the rotor and for producing an abnormal signal when the detected voltage is equal or higher than the reference voltage. In response to the abnormal signal, the rotor is rotated from a low speed. <IMAGE>