| 摘要 |
In order to minimise the costs of unauthorised telephone calls, the call duration is selectively limited. A device is used for this purpose which responds to the charge meter pulses and automatically terminates a call when the interval between the first two charge pulses is less than a pre-defined value, which allows a distinction to be made between tolerated local calls and unwanted long-distance calls. This device is simpler than a digit bar and is virtually impossible to bypass. |
