| 摘要 |
<p>A lifting machine (1) is monitored and controlled at a remote monitor center (2) through a general public line (3). The general public line (3) has plural kinds of line networks including a high-speed digital line network (32) for transmitting a large amount of information from the lifting machine to the center and including a low communication cost public line network (31) for transmitting a control command from the center to the lifting machine. For the large amount of information, line network selection means (14) selects the high-speed digital line network (32), and for the control command, the means (14) selects the low communication cost public line network (31), and then the means (14) causes transmission. For each line network, security means (15) encrypts information to be transmitted or restores the encrypted information, and a specific code added to the control command on the center side is verified and authenticated.</p> |
