This file is in the SYSTEM directory. This works exactly like INITTNCx.SYS,
but the parametres are sent to the TNC when the BBS is shut down. The file
can look like this:

 Y 1
 U 1 BBS ($c) was shut down for service $d $T.

 Y 1 means that only 1 station can connect my TNC now.
 U 1 means that the TNC will send this message to any user that connects
after the BBS has shut down.

If you use a PK-232, the same file would look like this:

 CTBBS ($c) was shut down for service $d $T.

 The  commands  sent  to  the  TNC,  are  the  commands  described in the 
documentation for the firmware you use, or in the documentation for PK-232,
DRSI, BPQ , KAM etc.