EIA-530

Currently known as TIA-530-A, but often called EIA-530, or RS-530, is a balanced serial interface standard that generally uses a 25-pin connector, originally created by the Telecommunications Industry Association.

Two types of interchange circuits ("signals" or "leads") between the DCE and DTE are defined in TIA-530: Category I, which uses the balanced characteristics of EIA-422, and Category II, which is the unbalanced EIA-423.

Revision A [2] changed these interchange circuits to Category II (para 4.3.6 and 4.3.7 of the standard[3]) and added a "Ring Indicator" on pin 22.

Confusion between the revisions has led to many incorrect wiring diagrams of this interface and most manufacturers still adhere to the original TIA-530 standard.

Care should be taken to ensure devices are of the same standard before connecting to avoid complications.