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[例1] 故障现象 双向呼叫对讲正常,但第一次摘机能拨打市话,挂机后再摘机即出现市话忙音,不能挂机。 分析与检修 反复摘挂机观察,每次摘机,绿色指示灯均能亮,每次挂机绿灯都能灭,说明主、手机的收发信号、呼叫信号均解调正常。偶然在摘机后不能挂机的情况下,将市话线从主机上拔下后再插上,又能挂机,从而判断为市话耦合电路失灵。用表测市话耦合继电器驱动三极管Q10的
[Example 1] Symptom Two-way calling intercom is normal, but the first off-hook to dial the local call, hang up and pick up the phone that busy tone, can not hang up. Analysis and maintenance repeated pick hook observation, each off-hook, the green light can be bright, each hang up the green light, indicating that the main cell phone signal transceiver, the call signal demodulation are normal. Occasionally in the off-hook situation can not be on the hook, the local telephone line unplugged from the host and then plug in, but also hang up, so as to determine the local city coupling circuit failure. Talk to the table using local speakers coupled relay drive transistor Q10