| 摘要 |
<p>AUTOMATIC CASSETTE HEAD DEMAGNETIZER An automatic electronic head demagnetizer, built into a standard cassette housing (1), includes a demagnetizer circuit (7) designed to produce a varying frequency signal within the audio range whereby the audio system of a standard cassette recorder may be used to produce an audio indication of proper demagnetizer functioning. The cassette housing (1) is provided with a resiliently mounted pressure pad (5) which forms part of an electrical switch connected to a circuitry (7) inside the cassette housing. When the cassette housing (1) is inserted into a conventional cassette tape recorder or playback machine and the "play" button thereof is depressed, the machine head moves into engagement with the pressure pad, pushing the latter into the cassette housing. As a result, the pressure pad (5), which is electrically conductive, makes electrical contact with another switch component (6)inside the cassette, housing, thereby closing an electrical switch in the housing. This activates the control circuit (7) for the demagnetizing inductor. In response to such activation, a demagnetizing field is established and then caused to decay from an initial maximum amplitude towards zero, whereas the frequency of the demagnetizing field is caused to increase from zero. After about 5 seconds, the user of the machine presses the "stop" button, thereby causing the machine head to cease pressing against the pressure head (5) and accordingly causing the switch to open and the demagnetizing operation to cease.</p> |
