ABBRER 133 Bus Connection Module

The EIA RS-485 Specification labels the data wires "A" and "B", but many manufacturers label their wires "+" and "-". In our experience, the "+" wire should be connected to the "A" line, and the "-" wire to the "B" line. When wiring RS-485 , use a shielded twisted pair cable with an internal impedance of 100-120Ω. Examples of recommended cables are CAT 5, Belden RS-485 (9841- 9844) and Alpha Wire (Alpha 6222-6230). A050325 Fig. 6.-3 Example on a cable shield connection The shield of the cables must be directly connected to ground in one of the nodes. In the other nodes the connection should be made via a capacitor, i.e. if the shield of the cable is connected to pin 1 in node 1, all the other nodes must be grounded using pin 2.

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