| 摘要 |
PROBLEM TO BE SOLVED: To provide a high convenience line selection device which automatically connects to an extension, when a public network is not connected to it. SOLUTION: The line selection device is provided with a connection detection means 3, a line selection controlling means 4, a line switching means 5, a selection key 6, and a line selecting means 2 having a key inhibiting means 7. When the public network (an external line) NT1 is not connected to a connector CN1, an L-level detection signal SD is supplied to the line selection control means 4 and the key inhibiting means 7, key information JG, JN by means of the operations of an extension button 6 or an external line button 6b of the selection key 6 is prevented, an extension network selection signal SN is supplied to the line switching means 5 at all times from the line selection control means 4. A CATV network (extension) NT2, to be automatically connected to an analog telephone TEL, is selected by invalidating the operations of the extension button 6 or the external line button 6b of the selection key 6 by connecting the CATV network (extension) NT2 (a codec 9 in Figure) to the analog telephone TEL. COPYRIGHT: (C)2004,JPO
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