| 摘要 |
PURPOSE:To form a small-sized and inexpensive information transmitting system by using a signal level of an n-value and another signal level representing that the signal is not transmitted. CONSTITUTION:A transmission circuit 9 of each terminal device 2 drives a transmission line 1 to a level V0 by an impedance Z0 sufficiently higher a transmission impedance Z and when all terminal devices 2 connected to the transmission line 1 are not in the transmitting state; since the level of the transmission line 1 is at V0, each terminal device 2 supervises normally the transmission line 1, discriminates the level V0 and detects the idle state of the transmission line. Since the transmission line 1 is driven to any of levels V1-Vn at the impedance Z at the transmission, when the relation of <<Z0/K is established, then at least one set of terminal device 2 starts transmission, and the transmission line 1 goes to any of the levels V1-Vn, and the receiving circuit 3 of the other terminal device 2 discriminates the level of n-value for attaining reception and detects that the transmission line 1 is in use at the same time. |
