摘要 |
<p>By the speaker detecting device, the test signal (DN) is supplied to the output terminal (D) to which the speaker (6) is to be connected. If a speaker (6) is connected to the output terminal (D), the test sound (DN) is output via the speaker. If no speaker is connected to the output terminal (D), no test sound is output. The test sound detecting unit (8) detects the test sound in the acoustic space (7) and compares the signal level of the test sound with the predetermined threshold level (TH2), thereby to judge whether or not a speaker (6) is connected to the output terminal (D).</p> |