Int 2F Fn D300  U - Telereplica - Installation Check                       [R]

   AX = D300h
   BX = 4562h
   CX = 2745h
   DX = serial port I/O base address??? (03F8h for v3.9)

Return: SI = segment of resident code
   AX = 251Dh
   BX = DF21h
   CX = F321h
   DX = ???