This object specifies the line signaling type that will be
used for the R2 line signaling.
. digital (1): The digital line signaling is typically used
for PCM systems. Only A and B bits are used to indicate
line signaling states, while C and D bits may be optionally
used.
. analog (2): The analog line signaling is typically used for
carrier systems. Only A bit is used to represent tone-on
and tone-off indication to signal the line signaling states,
while the B, C, and D bit are fixed.
. pulse (3): The Pulse type line signaling is typically used
for satellite links. It uses tones sent as pulses to
indicate line signaling states.