Hi hopefully someone can help out. I've built an ECG project based on AD6424AD. It's running on 9volt battery supply. Output to DAC and signal processing done in C.. I'm considering adding the optocoupler PS2506. Having difficulty understanding the resistance values required in this circuit. The high CTR of the device means only low current is needed at the LED. Any help would be much appreciated, I don't get to these resistor values with their datasheet. Thanks again..