The RS-232 standard was first introduced in 1962 by the Radio Sector of the EIA. The original DTEs (data terminal equipment) were electromechanical teletypewriters, and the original DCEs (data circuit-terminating equipment) were usually modems. For many years, an RS-232-compatible port was a standard feature for serial communications, such as modem connections, on many computers. The RS-232 standard is still used to connect industrial equipment (such as PLCs), console ports and special purpose equipment.

The IEEE RS-232 standard defines electrical, signal timing, and size connectors. Use of a common ground, limits RS-232 to applications with relatively short cables. RS-232 connection consisting only of transmit data, receive data, and ground. RS-232 protocol uses bipolar signal. Valid signals are ±3 to +15 volts, the ±3V range is not a valid RS-232 level. Data signals between -3V and -15V represents a logic 1. The logic 0 is represented by a voltage of between +3V and +15V.

RS-232

Standard

TIA-232-F

Cabling

Single ended

Connector

DB9

Network Topology

Point-to-point

Maximum Speed

115200 bps

Signaling

Unbalanced

Mark(1)

-5...-15

Space(0)

+5...+15

Signals

Full Duplex (Rx, TX)