Int 2F Fn 7F0C  - Prindir V9.0 - Set Echo State                            [P]

   AX = 7F0Ch
   DX = new state (00h echo off, 01h echo on)

Return: AX = status
       0000h successful

See Also: AX=7F00h"PRINDIR",AX=7F0Ah,AX=7F0Bh,AX=7F0Dh,AX=7F0Eh