Ok, if you enable this parameter,
when the BSC detects a HO towards a cell that belongs to ANOTHER BSC, then it sends a HO REQUIRED to the MSC.
In the HO REQUIRED, the field “Speech Version” will contain what is the current Speech Version of the call (which Codec…).
This allows to transmit this information to the target BSC, in order to do something ( ??? probably prepare TFO continuity, or keep the same codec in the target cell, at least ???)
But since it involves the MSC, you must ensure the MSC will properly transmit this parameter to the target BSC.