Vaisala WXT520 - Address Query Command (?); Acknowledge Active Command (A)

Chapter 7 __________________________________________________ Getting the Data Messages
VAISALA_______________________________________________________________________ 81
Address Query Command (?)
This command is used to query the address of the device on the bus.
If more than one sensor is connected to the bus, they will all respond,
causing a bus collision.
Command format: ?!
The response:
a<cr><lf>
Example (device address 0):
?!0<cr><lf>
Acknowledge Active Command (a)
This command is used to ensure that a device is responding to a data
recorder or another SDI-12 device. It asks a device to acknowledge its
presence on the SDI-12 bus.
Command format: a!
where
? = Address query command
! = Command terminator
where
a = Device address (default = 0)
<cr><lf> = Response terminator
where
a = Device address
! = Command terminator