| 摘要 |
<p>PURPOSE:To assure a detection for the termination of a tape regardless of the type of the tape, by varying the detecting sensitivity of an optical tape termination detecting circuit with interlocking to the switching action of a changeover switch which selects the type of a tape. CONSTITUTION:The irradiating light given from an LEDD1 is reflected to the magnetic tape part of a tape 12 and then received by a phototransistor TRQ1. A changeover switch S14 selects the type of a tape and has the positions corresponding to the normal, chrome and metal tapes respectively to switch the characteristics of a circuit (not shown in the diagram). A switch S15 interlocks the S14 and inserting selectively variable resistors R19-R21 into the circuit to vary the gain of amplification of an operational amplifier OP1. As a result, the gain of amplification is increased with the metal tape, etc. having a high reflection factor and decreased with the chrome tape, etc. having a low reflection factor respectively. Thus the highest level is set constant regardless of the type of the tape for the voltage which is differentiated by a capacitor C4 and a resistance R9. This prevents an erroneous detection for the termination of a tape.</p> |
