RS-232 is a Full-Duplex 3 wire serial communication standard originally developed back in the 1960's. The full RS-232C specification calls for a 25-pin connector and 22 wires for communication, however these are rarely needed by the devices in use today where most only need the Transmit (TX), Receive (RX), and Ground (GND) wires to communicate with each other. Because of this the most common connector you will see for RS-232 is the 9-pin DB9 Connector.

This is the DB9 "Male" connector, which is commonly found on older PCs, and is the connection that all of our USB to Serial adapters will mimic. It has two rows of pins, 5 on the top and 4 on the bottom. On each side is a "nut". The matching cable that connects will have screws on the sides that allows it to secure itself to the host. This is both a blesing and a curse. Unlike USB or other newers cable types it cannot be accidentally unplugged, however should somone trip over a cable the results could be disasterious.

The most common use for RS-232 communication today is for consumer GPS units, Stenograph Machines (court reporters), for monitoring of Uninterruptible Power Supplies (such as those from APC Corp.), and for interfacing with network switching equipment (such as those from Cisco Systems, Inc). RS-232 enabled products are typically found in consumer products, or enterprise IT products. While some industrial appliactions exist that use RS-232, they are rare, with most industrial appliactions using RS-422 or RS-485.