Hi David,
I can't seem to find, however, any consistency in the circuits I'm supposed to use. The datasheet's standard circuit uses 1uF capacitors; Maplin's circuit in the catalogue uses 22uF; the circuit here:
http://www.seattlerobotics.org/encoder/aug97/cable.html
...uses 0.1uF. Hardware's not my strong point. Can anyone clarify? How critical are these sizes?
Not my strong-point either, but here's another circuit diagram from the Hardware Recycling Initiative to throw into the pot. 0.1mF.
http://hri.sourceforge.net/tools/#uart
Cheers,
Ralph.