| 摘要 |
PROBLEM TO BE SOLVED: To reduce line usage charge by obtaining a state being the same as that where a computer device is directly connected to a subscriber line substantially and permitting the computer device to execute data communication with a public network. SOLUTION: When a telephone line is in an open state and also a calling signal is not detected, the telephone line Lt is free and usage possible so that a switch SW1 is changed-over into a b-contact side. Thus, a direct current supplied from a DC supply part 34 to a local line L1 is closed by starting data communication at the side of PC 20. Then the local line L1 is connected to the telephone line Lt, the direct current is supplied to the local line L1 not from the DC supply part 34 but from the subscriber exchange equipment of a telephone network, the same line connecting state is obtained after directly connecting PC 20 to the telephone network and data communication with the telephone line by PC 20 is enabled. In this case, it is continued till a DC detecting part 33 detects the opening of the local line L1. |
