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防止电话的盗用一般有两种办法:一是通过程控交换局采用呼出加锁的办法,自己用时再用密码开锁。加锁分为呼出加锁,长途呼出加锁,国际长途呼出加锁三种,一般多采用长途呼出加锁的做法;另一种是采用防盗用功能的话机。这里介绍的就是这种话机。 防盗话机一般分为提示型和干扰(制止)型两种。 1.提示型防盗 当有盗用话机与用户话机皆处在挂机状态时,电话回路呈现高阻抗。此时因有隔直电容器,直流回路不通,用户话机引入线处的电压在纵横制交换机为60伏,在程控交换机为48伏。如盗用话机取机,回路即降到低阻抗,直流电路接通,用户话机引入线处的电压下降到10伏左右。用户话机未摘机,通话回路尚未接
Prevent theft of the phone in general there are two ways: First, through the program-controlled exchange of outgoing lock method, when you use the password to unlock. Lock is divided into exhaled lock, long-distance outgoing lock, international long-distance dial-out lock three kinds, the general use of long-distance outgoing lock the practice; the other is the use of anti-theft features of the phone. Here is the introduction of this phone. Anti-theft phones are generally divided into prompt and interference (stop) type two. 1. Tip-type anti-theft When there are stolen phone and user phone are hanging in the state, the phone circuit presents a high impedance. At this point due to a blocking capacitor, the DC loop barrier, the user at the phone line voltage at the crossbar switch 60 volts, 48 volts in the program-controlled switches. If the theft machine take the machine, the circuit is reduced to low impedance, DC circuit connected, the user at the phone line voltage dropped to about 10 volts. User phone is not off the hook, the call loop is not yet connected