Frequently Asked Questions

RS232/RS485/RS422 QUESTIONS

5) WHAT ARE THE HANDSHAKE LINES ON AN RS232 DEVICE?

Answer: Handshake lines are used on an RS232 interface to control the flow of data between the DTE and the DCE. The handshake lines were included in the RS232 standard to accommodate the wide variety of telecommunications equipment in-use at the time of initiation of the standard in 1962. Most DTE and DCE equipment uses only a subset of the handshake lines. As many as 6 RS232 handshake lines are available: CTS (Clear To Send), RTS (Request To Send), DTR (Data Terminal Ready), DSR (Data Set Ready), DCD (Data Carrier Ready) and RI (Ring Indicator). The required RS232 handshake lines are controlled automatically on most of our RS232 to RS422 and RS232 to RS485 converters. RS422 and RS485 data flow auto-sensing auto-turnaround circuitry is built-in. On the RS422 or RS485 side, the circuitry automatically senses the direction of the data, and controls the handshake lines and data flow on the RS232 port appropriately.