INT 2F - Communicating Applications Specification - SUBMIT FILE TO SEND
        AX = CB15h
        DS:DX -> variable-length data area (see below)
Return: AX >= 0 event handle
           < 0  error code (see AX=CB01h)

Format of data area:
Offset  Size    Description
 00h    BYTE    transfer type
                00h = 200x200 dpi, fax mode
                01h = 100x200 dpi, fax mode
                02h = file transfer mode
                03h to 7Fh reserved
 01h    BYTE    text size
                00h = 80 columns
                01h = 132 columns
                02h to 7Fh reserved
 02h    WORD    time to send (DOS packed time format, see INT 21/AX=5700h)
 04h    WORD    date to send (DOS packed date format, see INT 21/AX=5700h)
 06h 32 BYTEs   ASCIZ destination name
 26h 80 BYTEs   ASCIZ name of file to send
 76h 47 BYTEs   ASCIZ phone number to dial
 A5h 64 BYTEs   ASCIZ application-specific tag string
 E5h    BYTE    reserved (00h)
 E6h    BYTE    cover page
                00h don't send cover page
                01h send cover page
                02h to 7Fh reserved
 E7h 23 BYTEs   reserved (zeros)
 FEh variable   ASCIZ string containing text of cover page (if cover page flag
                set to 01h)