Maybe digital link descriptor
Voice Encoding
This field is only valid for programming the voice encoding method of the CEPT Formatter II, DS1/T1 Formatter II (Universal T1/E1), and NSU cards. Possible values are "Nil" for no change, "ADI" for alternate digit inversion (even bits inverted), "Invert" for all bits inverted, and "Inverted ADI" for odd bits inverted.
NOTES
LA NSU (Universal T1/E1), set to "Inverted ADI" when calling from the SX-2000 FD to a MiVoice Business system (DSU to NSU).
NA NSU (Universal T1), set to "Invert".
NA NSU (Universal E1) direct connect to Universal E1, set to ADI.
UK NSU (Universal E1), set to "Nil".
UK NSU (Universal T1) direct connect to Universal T1, set to Invert
Embedded PRI: T1 in North America and E1 in Europe are set to "Nil" by default. However, if you experience noise on the trunks, set Voice Encoding to "Invert"
E1 in NA or T1 in Europe must have voice encoding set to "ADI".