if using C2811 router as Voice Gateway.
one IDAP connects to PSTN, while FXS/E&M/T1/E1 connects to PABX/phoneset.
Do IP need to configure for IDAP? if no, that mean there is no VOIP, so do PVDM still require?
Seems the call is only as analog but no IP?
Hence, do PVDM still required?