目前,一些单位由于电话费用居高不下,为了节省办公费用,减少电话费用支出,同时,也为了便于管理,有效地控制无权用户拨打长途电话,往往在电话机上加装了“锁控装置”,当有权用户打长途电话时,只要用专用钥匙打开锁控装置,即可打长途电话。下面就P/T兼容锁控电路工作原理及常见故障排除方法介绍如下: 一、工作原理电路如图1所示。CD4013B是一种双D型触发 At present, in order to save office expenses and reduce telephone charges, some units, as a result of high telephone charges, also effectively control the unauthorized users to make long-distance calls in order to facilitate management and often install “lock control devices” , When the right to make long distance calls, just use the special key to open the lock control device, you can make long distance calls. The following P / T compatible locking circuit works and common troubleshooting methods are described below: First, the working principle of the circuit shown in Figure 1. CD4013B is a double D-type trigger