Int 21H, AH=5FH, AL=01H

3.1 and higher

SET REDIRECTION MODE

  AX = 5F01h
  BL = redirection type
      03h printer
      04h disk drive
  BH = redirection state
      00h off
      01h on

CF set on error
  AX = error code (see #01680 at AH=59h/BX=0000h)
CF clear if successful

When redirection is off, the local device (if any) rather than the remote device is used. Calls INT 2F/AX=111Eh with AX on top of the stack

AX=5F00h - INT 2F/AX=111Eh - INT 60/AX=0002h

Text based on Ralf Brown Interrupt List Release 61