| 摘要 |
PURPOSE: A circuit for automatically transferring telephone lines is provided to connect a pair of telephone lines to terminals in parallel and to grant priority to either of them so that the priority terminal can freely seize and use lines even though the other terminal is using a line. CONSTITUTION: A circuit for automatically transferring telephone lines consists of photo couplers(PC1,PC2), a switch(SW1), transistors(Q1,Q2), and relays(RY1,RY2). Each photo coupler(PC1,PC2), connected to each of the telephone lines(LINE1,LINE2) connected with a telephone line(LINE) in parallel, is turned on when a terminal connected to its own telephone line is used. The switch(SW1) connects the collector of the photo transistor of either of the photo couplers(PC1,PC2) to the base of either of the transistors(Q1,Q2) according to a user's request. Each transistor(Q1,Q2) is turned on by the collector voltage of the photo transistor of each photo coupler(PC1,PC2). Each relay(RY1,RY2) controls each telephone line(LINE1,LINE2) according to the driving of each transistor(Q1,Q2) in order to control the use of each terminal.
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