Every technical information about the DBI3 and DBT3 you can find here.
Manual for 1.6 firmware
By turning the RMSS (Rotary Mode Select Switch) clockwise or counterclockwise you can set the DBI in 4 different modes:
OFF – Instrument is hard off
OP1 – Setup mode enabled
OP2 – Same as OP1 (for future use)
LOCK – Setup mode disabled
The NoSig indication in the right corner shows if the DBT3 (temperature sensor) is transmitting. When NoSig appears, the transmitter is not sending new temperature updates.