| 摘要 |
PURPOSE:To perform a backup operation, by setting one of POS terminals connected to a controller via a balanced transmission line as an equipment current in use and the other as a spare equipment, and performing the switching of the equipment current in use and the spare one by detecting the low impedance time of the line. CONSTITUTION:The POS terminals 1-n are connected to the controller 10 via the balanced transmission line 15. A pair of terminals 1 and 2 is formed, and one of them is designated as the equipment current in use and the other as the spare equipment, and a means 30 to detect whether or not the circuit 15 is at low impedance, and a means 40 to decide whether or not the low impedance time detected by the means 32 exceeds and continues over a regulated time are provided at the terminals 1 and 2, respectively. The equipment current in use in operating is separated from the line 15 by driving a switchins circuit 3 by the output of the means 40, and when the line 15 is set at high impedance, the spare equipment is operated, and when the line 15 is still set at the low impedance, a circuit 3 is recovered, and the equipment current in use is connected to the line 15 and operated. In such a way, it is possible to perform the backup operation by utilizing the spare equipment. |
