Output buffering and A/C device control

hi all, I understand the digital outputs of the ARduino are +5v, can supply 50ma, and can be configured as "open-collector" or have an internal pull-up resistor enabled.

I have quad triac A/C power control board I want to control. The inputs of the Quad triac card are 4n27 opto-isolators that require: - "9 to 12vdc control voltage @10mA - quote "any card that can deliver a control current of 10mA or higher" - quote " control cards with open-collector outputs"

The card has an input resistor called "Rx" which is 820 ohms if your input voltage is 9 to 15v. manual says if you have a 24v control voltage, change RX to 1.8k. Does this mean that I could use a LOWER resistor value, of around 400 ohms, and control directly from the Arduino output pins?

Also, should I buffer the outputs of the ARduino, with something like and SN7417 hex buffer chip?

Thanks much for any advice you may have. Cheers

can supply 50ma