Patent ID: 6956817

Claim:
A system transmitting a signal from one system to another system by utilizing plural lines comprising: communicating means for communicating the signal; first transmitting means for transmitting a first signal through a first line; inserting means for inserting a line switch signal which requests to switch a utilized line of another system into a second signal; second transmitting means for transmitting the second signal through a second line, and transmitting the line switch signal to another system after the utilized line was switched; switching means for switching the utilized line, and transmitting the signal between the communicating means and the first transmitting means, or between the communicating means and the second transmitting means; extracting means for extracting a line switch end signal which indicates the utilized line of another system from the second signal transmitted from another system side to the second transmitting means; and controlling means for controlling the switching means to return to the state before switching when the utilized lines of the system disagrees with the utilized line of another system, and controlling the switching means to keep the present state when the utilized line of the system agrees with the utilized line of another system.