This command checks that a device responds to a data recorder or another SDI-12 device. It asks device to acknowledge its presence on the SDI-12 bus.
Command format:
a!| a | Device address |
| ! | Command terminator |
Response:
a<cr><lf>| a | Device address |
| <cr><lf> | Response terminator |
Example:
0!0<cr><lf>