| 摘要 |
<p>PURPOSE:To improve transmission efficiency by associating an electromagnetic wave generating circuit and an electromagnetic wave receiving circuit to a microphone and speakers and controlling the output levels of the speakers with the circuits controlled by the receiving signal when both approach. CONSTITUTION:When a microphone 1 approaches to, e.g., 5 of speakers 5 thru 7, the electromagnetic wave of the burst signal such as of 30K Hz in the oscillation frequency by a control signal generator 3 and 1/10, etc. in duty is radiated from a transmission coil 2 and when this is received in a reception coil 8, an FET transistor 22 is turned ON by this receiving signal, then a voltage of a specified level is obtainable in a resistance 23. As a result, a relay, etc. are energized to cut off or reduce the output of the speaker 5. Thereby, the output of only the speaker in proximity to the microphone is controlled and howling is prevented, hence transmission efficiency may be improved.</p> |
