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