Prolific USB-Serial/Mac OSX

I've been using the keyspan dongle for ages.

Your problem doesn't sound like a dongle problem but maybe your terminal emulation program. What are you using? Might want to take a look at ZTerm

Using ZTerm both on the PowerBook with Prolific USB-Serial as well as on the Legacy Mac with built-in serial. Also tried QuickTerm with the same results. Tried both USB ports on the PowerBook, no change. While it may be the terminal emulation program, I can't for the life of me figure out what's causing it. And again, it works fine on OS 9 machine with the same carbon-version of ZTerm.

Have you tried using a null modem adapter? They cost less than $5 and will possibly fix this for you. If not, you will have to make your own cable:

-Wil

The switch thinks it is connected to a modem and is sending modem configuration strings.

I am not an expert with modems and I have never configured one to work on a Cisco.

There seem two possibilities.

1. The Cisco is configured to do this.

1. Maybe your serial port is toggling some of the control lines that is making the cisco think that it is connected to a modem.

1900 is pretty old and the usual Cisco recovery processes are not applicable so I can't help further.

You could always try to connect to it using modems. Might be worth finding out what these particular strings mean.

Yes, I tried this and got absolutely nothing. I think Bod43 is on the right track when he says the switch thinks it's connecting via modem. I just don't know how to disable/fix that.