This section applies to Digi products equipped with EIA-422 asynchronous interfaces.
EIA-422 interface cables should be shielded twisted-pair cables. Each signal requires two leads (one twisted pair of wires) to complete a balanced voltage digital circuit. The shield should be connected to the Chassis Ground of the devices at both ends of the interface cable.
The EIA-422 interface provides four signals: Transmitted Data (TxD), Received Data (RxD), Request To Send (RTS) and Clear To Send (CTS). The functions of these signals are identical to their EIA-232 counterparts.
EIA-422 interface cables must provide a ground path between the devices to be connected. This insures the integrity of data transfers and control signals. This should be connected to the Chassis Ground of each device. Digi recommends using the cable shield for this purpose.