| 摘要 |
A device for preventing calls from a network interface device, disposed between a customer's premise equipment and that portion of a telephone loop owned by a telephone company connecting the network interface device to a telephone central office, by periodically disconnecting that portion of the telephone loop owned by the telephone company from the subscriber's premises equipment every few seconds. An unauthorized person can get dial tone and can attempt to dial a number, but before the called party can answer, the line is disconnected. Dial tone will appear again after a given period of time, the cycle of dial tone-no dial tone continuing indefinitely. A premise owner may test the integrity of the loop between the owner's premises and the central office in a conventional manner notwithstanding.
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