INT 15h,  44h (68)       Activate/Deactivate Modem Power          Convertible

    Activates or deactivates the PC Convertible internal modem.

       On entry:      AH         44h
                      AL         Modem power state
                                 00h - Turn internal modem power off
                                 01h - Turn internal modem power on

       Returns:       Carry      Set if error, else cleared
                      AL         0 if successful, else non-0

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       Notes:         This service is available only for the PC
                      Convertible.

                      If the internal modem power is turned on (AL = 01h),
                      it is initialized to the current settings found in
                      the modem profile. See Service 40h for more
                      information on the modem profile.