| 摘要 |
PURPOSE:To make a call possible even when only one is normal among plural talking channels, by transmitting not only talking signals but also channel selecting data signals through the talking channels. CONSTITUTION:When channel selecting data is sent to a called station, the data is sent by alternately inputting signals into input terminals 6 and 8 and alternately inverting the polarities of talking channels (a) and (b). Namely, when the data is H, H is given to the terminal 6 and L is given to the terminal 8 and, when the data is L, L is given to the terminal 6 and H is given to the terminal 8. Therefore, the talking channels (a) and (b) are alternately inverted and the channel selecting data is sent. When a call is started, a talking circuit is connected with the talking channels (a) and (b) by setting an input terminal 5 to H and turning transistors Tr1 and Tr2 on and, at the same time, it is informed other offices that the talking channels (a) and (b) are used by turning transistors Tr5 and Tr6 on and setting the talking channel (a) to (-) and talking channel (b) to (+). |
