Question about notation used in a schematic for ADM-3A

Thread Starter


Joined Feb 9, 2016
Hi, I've been debugging an ADM-3A serial terminal for a while. When studying the schematics, I found some notations that I do not know what they represent. As an example, please see this image here that I cropped from the maintenance manual:

adm-3a schematics sample.png

What does the 280 here represent? It doesn't seem like a standard notation. Nor can't I figure out from the context what it means. Maybe it's just something internal to the manufacturer, but maybe it's a hint that I'm missing. Anyone knows?