51
&T5
Denies RDL request from remote modem
&T6
Initiate remote digital loopback.
&T7
Starts remote digital loopback with self test.
&T8
Initiate Local Analog Loopback with self test.
&Un
Trellis coding (Default=0)
&U0
Enables Trellis coding with QAM as fallback
&U1
QAM modulation only
