Glossary · Automation fundamentals, platforms and components
Rx (receive)
Also known as: RX, Receive data (RxD)
German: Rx
In data communication, Rx is the common abbreviation for "receive" or the receive line or channel of an interface, as opposed to Tx for "transmit". It labels receive pins, LEDs, counters and signals on serial ports, network interfaces and radio modules.
- Automation components
In one sentence
Rx is the abbreviation for receive, the receive line or channel of an interface, as opposed to Tx for transmit.
Example
The Rx LED on the gateway flashes, but the Tx LED stays dark, showing that requests arrive but the device does not answer.
How it applies
- Commissioning: Rx and Tx LEDs and counters are quick Diagnostics for communication problems: no Rx activity points to wiring or the remote side, Rx without Tx to configuration or addressing.
- Wiring: On point-to-point serial links such as RS-232, one device's Tx connects to the other's Rx. Whether a cable needs to cross the lines depends on whether both ends are the same device type.
- Documentation: Pin assignments should state from whose point of view Rx and Tx are named (device or connected equipment). This small detail avoids many wiring errors.
Rx vs. Tx
Rx is the receive direction, Tx the transmit direction. On a two-wire RS-485 bus, both share one pair and the direction switches.