The actual transmission mode of the ATU-C.
During ADSL line initialization, the ADSL
Transceiver Unit - Remote terminal end (ATU-R)
will determine the mode used for the link.
This value will be limited a single transmission
mode that is a subset of those modes enabled
by the ATU-C and denoted by
adslLineTransAtucConfig. After an initialization
has occurred, its mode is saved as the 'Current'
mode and is persistence should the link go
down. This object returns 0 (i.e. BITS with no
mode bit set) if the mode is not known.