I think I just made a big mistake. Im studying for the CCENT and I purchased a catalyst 1900 (WS-C1924-A) and a 2501 router from Ebay. Using Tera Term and a rollover cable I was successfully able to connect to the console port of the router and configure the terminal. Next I attached the same rollover cable to the console port on the 1900 switch. After the POST all that would appear on Tera Term was ATQ0H0 and ATQ0Z0. So after many hours I found out that hold down the MODE button on the switch and power cycle the switch I would be put directly in to Cisco Systems Diagnostic Console.
Diagnostic Console - Systems Engineering
Operation firmware version: 9.00.04 Status: valid
Boot firmware version: 3.10
[C] Continue with standard system start up
[U] Upgrade operation firmware (XMODEM)
[S] System debug interface
This worked just fine and the text was displayed correct on the screen. I tried this command [R] Reset main console RS232 interface to 9600,8,1,N but this didnt fix the ATQ0H0 problem I was having. Then I had the bright idea to [U] Upgrade operation firmware (XMODEM) even though I didnt have a upgrade file. And this is what happened below.
Diagnostic Console - Systems Engineering
Operation firmware version: 0.00.00 Status: invalid
Boot firmware version: 3.10
WARNING!!! Operation firmware is invalid.
Upgrade firmware to enable switch operation.
[U] Upgrade operation firmware (XMODEM)
[S] System debug interface
What options do I have to fix this?
