| 摘要 |
The system comprises transceivers employing identical modems, one located at a fixed position and connected to the wire and one on a vehicle guided along the wire. The transceiver's specialized modems may be connected to a central host which may be a computer, to a programmable controller, or to a communications bus as required. Additional transceivers may be connected to the communications bus for communication between the central host and additional wires. All central host signals are transmitted to all wire connected modems and sent out on all wires. All signals from vehicle modems are transmitted back to the central host. Each transceiver is adapted to employ one or more identical modem, each connected to a different wire. Communication between the wire and a vehicle is by means of an inductive coupler employing ferrite rods which is designed such that the transfer function from the fixed modem to the vehicle mounted modem is substantially identical to the transfer function from the vehicle modem to the fixed modem. The vehicles may be wired guided vehicles controlled by low frequency signals on the wire. In this case a special coupling circuit is employed so that no modification is required in the equipment normally used to signal along the wire for controlling the vehicle or in the modems connected to the wire. The modems employ state machines for on-off frequency keying detection, a powerful protocol for error free transmission, a specialized circuit that presents different impedances during transmission and reception, and a switching circuit for providing high damping on transmission and low damping on reception. |
