rdcxxxxx 4p - Full 4 of 4 ground 1 to 2.5 KV galvanic/optical isolation

4 of 4 ground isolation means all data grounds are 100% isolated from each other and the power supply ground. Like 3 of 3 ground design, this is always the safest design option. All redundancy - supporting products (hubs, arbitrators etc) are based on this design.

rdcxxxxx 3p - Full 3 of 3 ground 2500v galvanic/optical isolation

3 of 3 ground isolation means both data grounds are 100% isolated from each other and the power supply ground. In DC powered systems, this is always the safest design option. All RDC products are engineered with this design in mind.

rdcxxxxx 2p - Partial 2 of 3 ground 2500v galvanic/optical isolation

2 of 3 ground isolation means one data ground is 100% isolated from both the other data ground and the power supply ground, while the other data ground is sharing the same as the power supply ground. RDC products of this design can be used when both the local device and RDC device share the same power supply (and therefore the same ground). Most "opto-isolated" data communication products on the market are built on this design, which will cause issues if the local device and RDC device are on different grounds.

rdcxxxxx 1p - Non-isolated converter

Non-isolated means this converter assumes the electrical data comm ground is the same as the power supply ground. This assumption is Ok if both the device and converter share the same power supply (and therefore the same ground), but it will cause problems if they have subtly different grounds.

rdcxxxxx 2p - Full 2 of 2 ground 2500v galvanic/optical isolation

Full 2 of 2 ground isolation means the electrical data comm ground is 100% isolated from the power supply ground. In DC powered systems, this is always the safest design option.