Question about modems

Alexandre Souza alexandre.tabajara at
Wed Nov 13 07:47:03 CST 2019

Jim, its a long time I don't use it, but I've used other configurations 
beyond 8N1 and I remember when you put the modem in 7E1 it mirrored the 
configuration of the other side. If you had a vax with a 2400 7E1 port, 
you gotta have in the terminal 2400 7E1

So, you gotta match the configuration of the other side

Hope that helps!

Em 13/11/2019 04:25, Jim Brain via cctalk escreveu:
> I am the author of tcpser, a UNIX/Windows program that emulates a Hayes 
> modem.
> Some time ago, Chris Osborn (FozzTexx) forked a copy of my project to 
> fix some bugs and he also added in some parity code, which looks to 
> strip parity from the incoming serial connection (in the case that the 
> serial port is set as 8N1 and the computer attached to it sends in 7E1 
> or similar.
> I am working to merge in all of his changes into the mainline codebase, 
> but I am unclear on prpper Hayes behavior.  His Readme says:
> "I also made the modem routines automatically detect parity and ignore
> it in AT commands and print out modem responses in matching
> parity. Parity is *not* stripped when sending data over the
> connection, which is how a real modem behaves. This may or may not be
> what you want. Some servers will expect an 8 bit connection and may
> not work."
> Did Hayes modem really do that?  I thought most later modems self 
> detected parity and speed and thus would have switched both the comm on 
> the serial port and the data sent to the other side in the same parity 
> (if the terminal was 7E1, the modem would configure as 7E1 and send 7 
> bit data to the other side.
> But, maybe real modems did as Chris notes. Anyone have guidance on 
> this?  The goal of tcpser is to emulate a Hayes modem as much as 
> possible, but I never really thought about mismatched parity on the 
> RS232 line and how to deal with it.
> Jim

---8<---Corte Aqui---8<---

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