| 摘要 |
PURPOSE:To perform opposing communication between secondary stations, by semi-duplex opposing communication between the secondary stations through the use of transmission data lines. CONSTITUTION:When an opposing communication mode signal S1 is supplied, a switching circuit 6 changes over the output from the output of a line receiver 1 to the output of a line receiver 4. The signal S1 is generated when a switch of secondary stations DTE 1 and 2 is closed. A tri-state line driver 3 is activated to enable to output a transmission data D when a transmission enable signal S2 is applied, and is at high impedance while no signal S2 is supplied and disconnected from a line L2. The signal S2 is supplied while the secondary stations DTE 1 and 2 are at transmission mode. The transmission of a transmission request RS is inhibited with the AND gate while the secondary stations DTE are set to the opposing communication mode even if they enter the transmission mode. The data SD can always to possible for transmission when a transmission enable signal CS is applied in case of the normal mode through OR and AND gates and in case of the opposing communication mode. |
