In article <[log in to unmask]>,
[log in to unmask] (Dennis S. Keeler) says:
>
>        Something is different about the modems.
So True.  We have real 14.4 modems with lapdm and mnp level 5 service.
>        This is all fine and great, but YModem file transfers no longer work
>for me. (I don't have a Zmodem client.) I do everything as I used to: 8-N-1,
>miavx1, etc. Then I use the command sb -ak text.file. Everything goes great
>until I reach 16118 bytes. Then the transfer hangs, no matter what the file.
>Any clues? Any workarounds? Thanks, I'd hate to start using Kermit again!
More than a clue, I'm rather certain that I know what is wrong.
This is a classic flow control problem.  Once you allow for compression
the modems are capable of burst rate to 14.4 x 4 = 56kbps transfer.
Our end is using hardware flow control so that you can transfer
binary data.  Your end is probably not doing flow control.  To use
flow control
1.  You must have a modem cable with pins 4,5 connected straigh through
    or have an internal modem.
2.  Your software must have hardware flow control support.
3.  The modem must know that hardware flow control is to be used.
 
Your workarounds include:
A.  Figure out the above for maximum service.
B.  Dial the old modems.
The old 9600bps modems are now at 2161.  You can call them and receive
the "old" service.
C.  Use supported sofware, e.g. Kermit.  I know the vax client is old.
D.  Dial the new modems but configure your modem to request no data
    Compression.  If your DTE local rate is 19.2, this will at least
    give you 14.4 service.
Some common "Hayes" compatible AT commands that may work on your modem:
(All preceeded by AT and optionally followed by D4999)
For flow control:
&K0 disable flow control
&K1 enable RTS/CTS flow control
&K2 enable XON/XOFF flow control
For connection mode:
&Q0 Select asynchronous non-Error correcting mode
&Q5 Select V.42 error control  <==  requires flow control.
&Q8 Select alternate EC mode (i.e. MNP)
 
Give me a call at 6237 or send email to [log in to unmask]
to pursue this further.
 
I'm sorry you were inconvenienced.
 
Joe Simpson