Using a question mark (?) as the address character causes the WLTS to respond with the acknowledge active 'a!' command where 'a' represents the WLTS address. A typical command/reply would be: ?!/0<CR><LF>. The bold-faced characters are sent to the WLTS; the normal type-face is the WLTS's reply. In this case the WLTS address is "0". This command is good for determining the WLTS address, if it is the only sensor connected on the SDI-12 network.