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目前,电话机采用锁“0”的方式有两种:一是锁“0”以后,拨打首位为“0”的号码时,电话机不发号;二是拨打首位为“0”的号码时,话机可以把“0”发出,但以后再拨其他号码时不能发出,或发出首位“0”号后话机即自行挂断。本电路的锁“0”方式为第二种。由于现在的电话机大多是P/T兼容的,因此,单独的脉冲锁“0”或双音频锁“0”电路已失去意义,即锁“0”电路也应该是P/T兼容的。 本电路的另一个特点是,给电话机增加锁“0”功能时,无须改动话机内部电路,制作简单,因而适用范围广。
At present, there are two ways for the telephone to lock the “0”: first, after the “0” is locked, when the first digit is “0”, the telephone does not send a number; secondly, when dialing the number “0” , The phone can send out “0”, but can not send it when dialing other numbers in the future, or hang up after the first “0” phone number is released. The circuit lock “0” for the second way. Since most telephones today are P / T compatible, the separate pulse lock “0” or dual tone lock “0” circuit has no meaning, ie the lock “0” circuit should also be P / T compatible. Another feature of this circuit is that when the lock is added to the phone, the internal circuit of the phone does not need to be changed and the manufacture is simple. Therefore, it is applicable to a wide range of applications.