INT 2F U - DOS 4+ ANSI.SYS internal - MISCELLANEOUS REQUESTS
AX = 1A02h
DS:DX -> parameter block (see below)
Note:   DOS 5.0 chains to previous handler if AL > 02h on call

Format of parameter block:
Offset  Size    Description
00h    BYTE    subfunction
00h set/reset interlock
01h get /L flag
01h    BYTE    interlock state
00h=reset, 01h=set
This interlock prevents some of the ANSI.SYS post-processing
in its hook onto INT 10, AH=00h mode set
02h    BYTE    (returned)
00h if /L not in effect
01h if /L in effect

See also: 2F1A01

2F1A02 - DOS 4+ ANSI.SYS internal - MISCELLANEOUS REQUESTS