[kreutz]

Originally Posted by LeissKG Yes, the HCPL2231 does not need a pullup on the output ( stated in bold on the first page of the datasheet under features ). It can directly drive 4 TTL loads. It should work with the pullups in the circuit if the resistor value is not to low. The only difference should be slightly slower slopes of the signal. Klaus Leiss

True, but your UHU board will require both pull-up resistors if you are using a 74HC14 chip instead of the 74HCT14 or a plain 7414N (or 74LS14) chip.

Kreutz.