The line coding present on the physical interface This object
is only present for DS1/E1 interfaces.
'ami' indicates alternate mark inversion (AMI) line code
on the DS1/E1 interface.
'b8zs' indicates B8ZS line code on the physical interface and
applies only to DS1 interfaces.
'hdb3' indicates HDB3 line code on the physical interface and
applies only to E1 interfaces.