| 摘要 |
<p>PURPOSE:To surely perform protecting operation for everpower input without degrading the sound guality of acoustic signal by providing an independent detection coil to a step up transformer and operating protection circuit with the detection signal of the voltage corresponding to the electric signal being supplied to the primary side coil. CONSTITUTION:The detection signal by the coil 26c of the voltage corresponding to the electic signal suplied to the primary side coil 26a is full-wave rectified with a full-wave rectifier circuit 29 connected to the detection coil 26c independently provided to a step up transformer 26 and the output signal thereof is supplied to a peak holding circuit 21. The circuit 21 hold the peal hold level of the rectified output signal and supplies the resultant peak hold signal to a relay drving circuit 22. The circuit 22, which consists of a Schmitt trigger circuit having the threshold value corresponding to the permissible input level of a condenser type headphone, sends exciting current to the relay coil 24 to cause a switch 28 to be opened when the peak value of the detection signal exceeds the threshold value. Threrby, protecting operation may be surely performed without degrading the sound quality of the acoustic signal.</p> |
