INT 15 - Compaq SLT/286 - Modify Power Conservation/Modem Configuration
        AX = 4601h
        BL = system inactivity timeout (1-21 minutes)
           = FFh do not change
        CL = video display inactivity timeout (1-63 minutes)
           = FFh do not change
        DL = current fixed disk drive inactivity timeout (1-21 minutes)
           = FFh do not change
        DH = 00h turn modem OFF
           = 01h turn modem ON
           = FFh do not change modem state
Return: CF clear if successful
            AH = 00h
            BL = current system inactivity timeout (1-21 minutes)
            CL = current video display inactivity timeout (1-63 minutes)
            DL = current fixed disk drive inactivity timeout (1-21 minutes)
            DH = FFh modem state unchanged
               = 00h modem turned OFF
               = 01h modem turned ON
        CF set on error
            AH = 01h input is out of range
               = 02h - No modem present
SeeAlso: INT 77