| 摘要 |
<p>A stand-alone toll-barring device powered from the telephone line voltage or from an external supply. In its basic form it comprises means to recognise a user's personal identification number (PIN) as it is dialled in from a telephone or similar peripheral device, means to recall rights (if any) corresponding to that PIN from a memory table, and means to assess whether a number being dialled just after entry of the PIN is permitted under those rights. Emergency numbers and incoming calls are not barred. If the number is not permitted the call is immediately interrupted. Reprogramming of the data is provided by means of a further PIN. The device may be installed within a telephone or across fixed telecommunications wiring installations within a building. Should a larger range of permitted or denied numbers be required, multiple devices can be used in series.</p> |
