After some extensive testing, we concluded is that you are better off using the
AppleFax application for file transfers instead of using third-party terminal
software. Third-party software does work, but it is much slower.
The AppleFax Modem has built-in error correction, rendering the error
correction performed by MicroPhone, Red Ryder, MacTerminal, and so on
redundant. Furthermore, adding those additional layers of protocols and error
correction on top of the built-in error correction slows your transmissions
down and potentially subjects you to timeout errors (which is probably what you
are encountering), compounded by any noise on the lines.
For example, transmitting a .5MB file with the AppleFax application required
approximately 14 minutes. Transmitting that same file using MicroPhone II 2.0
using their YMODEM/MacBinary Protocol Transfer Setting was stated by the
program's status screen to require over 400 minutes! (Transmitting the same
file using YMODEM-G would take approximately 3 hours.)
We didn't wait the nearly 7 hours to verify that it would take that long,
because that status screen has been relatively accurate in the past. We did,
however, monitor the file transfer for 20 minutes and multiplied the remaining
number of bytes to be transferred by the transfer rate. We observed the
extremely slow transfer rate and are convinced it would take a very long time.
During the 20 minutes we monitored the file transfer, there were no errors
reported, nor were there any errors reported with the numerous other small
files we transferred using many of the other MicroPhone transfer settings.
Though the files transferred successfully, the file transfers took much longer
than when using the AppleFax software.
If you want to continue using MicroPhone or MacTerminal, we recommend using
YMODEM-G or MacBinary, respectively, as they do error correction less often
than the other options and don't use the other additional error correction
options, like CRC.