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在日常的电话机修理中,常遇到由于开关管损坏引起的故障,这类故障主要表现为“三无”,即“无接收,无发送,不拨号”。现以市场上比较流行的HA9888P/T话机为例作一简单介绍。 查该机电路图可知,V6(2N5401)与V7(2N5551)分别为PNP、NPN型三极管,它们构成了脉冲与双音频开关电路。由程控交换机输出的48V电压,
In the daily telephone repair, often encountered due to damage caused by the switch, such failures mainly as “three noes”, that is, “no reception, no transmission, do not dial.” Now the market more popular HA9888P / T phone for example for a brief introduction. Check the circuit diagram shows, V6 (2N5401) and V7 (2N5551) were PNP, NPN-type transistor, which constitutes a pulse and dual audio switching circuit. Programmable switch output 48V voltage,