This is very interesting thanks,

"Some older IBM Think Pads had comm ports that did not meet the true RS-232 specifications for data transfer. They operated at slightly different voltage ranges."


As it was a IBM Thinkpad that was being used.

1) I'm using 12V from a Computer Power Supply.

2 ...

Hello,

I'm current looking to use these devices in a mobile application and communicate with a PLC.

I have 2 Extended Range displays here, ones a VFD and a PLED.

My problem lies in the communication.

I have failed several attempts to communicate with either of these displays over RS-232.

My ...