| # fx set-relay | |
| Actuates the state of an external relay by writing a single byte to \|tty\|. | |
| ```none | |
| usage: fx set-relay [--off|--on] /dev/ttyUSB0 | |
| Turn on or off a USB-connected relay on the specified device. | |
| ``` | |
| [set-relay source code](https://cs.opensource.google/fuchsia/fuchsia/+/main:tools/devshell/contrib/set-relay) |