Communicating Applications Spec - Submit a task

        Entry:
          AX = CB01h
          DS:DX -> ASCIZ name of task control file
        Return:
          AX >= 0: event handle
              < 0: error code

        Note:   files needed for an event must be kept until task is
                complete or error

        Error codes (AH = class, AL = subcode, value passed back is
        2's complement):

  Class 00h     --- FAX warnings
        Subcode 00h     no error
                02h     bad scanline count
                03h     page sent with errors, could not retransmit
                04h     received data lost
                05h     invalid or missing logo file
                06h     filename does not match nonstandard format (NSF) header
                07h     file size does not match NSF header
  Class 01h     --- DOS warnings (data was sent)
        Subcode 01h     invalid function
                05h     access denied
                06h     invalid handle
                others  see INT 21/AH=59h
  Class 02h     --- fatal errors (data not sent)
        Subcode 00h     multiplex handler failed
                01h     unknown command
                02h     bad event handle
                03h     FIND NEXT attempted before FIND FIRST
                04h     no more events
                07h     invalid queue type
                08h     bad control file
                09h     communication board busy
                0Ah     invalid command parameter
                0Bh     can't uninstall resident code
                0Ch     file exists
                80h     unknown task type
                81h     bad phone number
                82h     bad .PCX file header
                83h     unexpected EOF
                84h     unexpected disconnect
                85h     too many dialing retries
                86h     no file specified for send
                87h     communication board timeout
                88h     received too many pages (>1023) of data
                89h     manual connect initiated too long ago
                8Ah     hardware command set error
                8Bh     bad NonStandard Format (NSF) header file
  Class 03h     --- fatal DOS errors
        Subcode 02h     file not found
                03h     path not found
                others  see INT 21/AH=59h
  Class 04h     --- FAX errors
        Subcode 03h     other FAX machine incompatible
                5Eh     other FAX machine jammed