Returns 2 bytes wide answer with the voltage at the LAI.
FRC user-data has the following format:
UserData[0] 0x4A (equals to the PNUM).
UserData[1] Reserved. Must equal to 0.
Returned 2 bytes wide FRC value has the same format as Volt parameter at the DPA response of Set LAI + 0x8000 (see Extra-low voltage FRC).