Ah. Okay. Thanks, Ray and Nick.
Yes, I realised the resistors aren't a potential divider. I wasn't sure how much of a voltage drop there'd be across the 22k resistor due to the input current though... I see page 43 of part 1 of the manual does say to use the same circuit for both cables.
Does the AXE027 USB cable have 5V TTL output levels, as I assumed, or are they higher to make it more like the output of the old serial cable?
Ray,
I hadn't considered the Java applet might just have run out of memory. Mine's almost full most of the time so that could be the reason. I'll have to try it without so many tabs open in the browser, probably in a different browser. I got it to accept a circuit by starting again but giving it a square wave or AC input doesn't seem to do anything. Maybe I'm just missing something.