'none' indicates that no bits are reserved for
signaling on this channel.
'robbedBit' indicates that T1 Robbed Bit Sig-
naling is in use.
'bitOriented' indicates that E1 Channel Asso-
ciated Signaling is in use.
'messageOriented' indicates that Common Chan-
nel Signaling is in use either on channel 16 of
an E1 link or channel 24 of a T1.