MTP2:Normal Proving
From TBwiki
The 'Proving normal timer' parameter (specifies the normal proving period timer value. It is only used for ITU and ANSI link types and is not used for the TTC and NTT link types.
The typical value is 8200 milliseconds (8.2 seconds) for ITU and 2300 milliseconds (2.3 seconds) for ANSI.
Note: A value of '0' is not permitted.