login with telnet. At the prompt type help. you will see: normal mode commands:

normal mode commands:
        clear           ---     clear screen
        exit            ---     leave to the previous mode
        help            ---     help info
        history         ---     show history commands
        logout          ---     logout cli model
config mode commands:
        config          ---     enter config mode
        adsl            ---     config adsl
        igmp            ---     igmp config
        wan             ---     wan config
        wlctl           ---     wireless config
        iptv            ---     iptv config
        lan             ---     lan config
        dev             ---     device control
        debug           ---     debug cmd

 now for more commands simply type e.g. dev and you will see that dev reboot will give you a reboot

@guydu13 I have only these available options for "adsl" command. I think there should be an "adsl configure" option to set the SNR value.
 

TP-Link(conf)#adsl
          adsl show info
          adsl show status
cmd:SUCC
TP-Link(conf)#