FaxBack Port Server - Manual - Manual (Page 51)

721F Cause 31, Normal unspecified: The TDM network rejected the call, or terminated a connected call with a
Q.850 cause code 31. Q.850 remarks that “call failure information indicating the failure of a call due to the
lapse of a timeout or a fault not covered by specific causes (examples: expiry of timers Q.764 not covered by
specific causes, release of interconnected circuit, etc.).”
7222 Cause 33, No circuit/channel available: The TDM network lacks capacity to handle this call. This can be due
to network congestion or a lack of inter‐carrier channels to a specific country or NPA/NXX.
726F Cause 111, Protocol error unspecified: The TDM network could not connect the call because of an
unspecified fault.
AudioCodes MediaPack FXO: These devices will return a protocol error unspecified if it does not detect
dial tone.