RS-232 Mechanical

Each line in an RS-232 interface is assigned a pin number for the various connectors that RS-232 can use. The nine primary lines, and their assignments in DB-9 and DB-25 connectors, are shown below.

RS-232 Cable Connections

The tables below show RS-232 wiring connections for straight cables (DTE-to-DCE) and crossover cables (DCE-to-DCE), when connecting DB-9 connectors to DB-9 connectors, DB-9 connectors to DB-25 connectors, and DB-25 to DB-25 connectors.

 These diagrams cover most scenarios. But wait! There is more to say on crossover cables, specifically. While this article shows three crossover configurations (for DB-9 to DB-9, DB-9 to DB-25, and DB-25 to DB-25 pairings), there are in fact more versions. This information will matter to users in some contexts, so read on. In the next article we will cover crossover cabling fully.