| 摘要 |
PURPOSE:To execute data communication at a high speed with a minimum data frame number by transmitting signals RS-232CRS, CS and CD to need immediate response between a data terminal and a MODEM with using the F bit of an envelope type data frame and an S bit. CONSTITUTION:A data terminal 15 is connected through an NCU/MODEM 14 to a public telephone network 13, automatically responds to a truck line terminating and a channel is switched to a data terminal side. A control circuit 5 of an exchange obtains a pair MODEM ER signal as ON by a pushing down the data key of a digital telephone set 2 and between a line 8 and a truck line trunk 12, a channel connecting between a line 9 and a data adapter 3 is executed. The control circuit 5 executes the control of an F bit and an S bit in a digital signal transmitting path envelope type data frame. Thus, a control signal transmission can be immediately executed.
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