| 摘要 |
PROBLEM TO BE SOLVED: To allow a broadcast device to detect a short circuit of loudspeaker lines. SOLUTION: When a short circuit takes place in any of each of loudspeaker lines 2, 2,..., an output current of an amplifier 3 far exceeds its rated current and reaches an overcurrent state. A current detection circuit 35 in the amplifier 3 detects this overcurrent. When the current detection circuit 35 detects an overcurrent, the circuit 35 generates an overcurrent detection signal and gives it to a CPU 5. The CPU 5 receiving the overcurrent detection signal recognizes the occurrence of a short circuit in any of the speaker lines 2. Then the CPU 5 sequentially turns on/off each of relay switch circuits 4, 4,... to sequentially and singly connect each of the loudspeaker lines 2, 2,... to the amplifier 3 so as to confirm whether or not the amplifier 3 supplies the current detection signal in this process. Thus, the CPU 5 locates the short circuit of any loudspeaker line 2 and displays the result on a display section 7.
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