This is the operational loopback type for the HDSL.
loopbacks setting:
1 : Smartjack - loopback to network at remote line unit.
2 : Loopback to network at local line unit.
3 : Loopback to network at remote line unit.
4 : Loopback to customer at local line unit.
5 : Loopback to customer at remote line unit.
6 : Loopback to customer at first doubler.
7 : Loopback to customer at second doubler.
8 : Loopback to network at first doubler.
9 : Loopback to network at second doubler.
10: No loopback (turn loopback off).