yaafm:
Just been reading up on Grumpy_Mike's open collectors - seems that something like a 7407 would be the way to go? If so am I correct in thinking I can forget about current limiting resistors i.e. the buffers on their own will suffice?
Arduinos can do "open collector". You simply switch the pin between OUTPUT_LOW and INPUT_NOPULLUP (ie. change the port direction bit, "DDR") instead of going OUTPUT_LOW<->OUTPUT_HIGH.