>Hi,
>
>Since there has been some discussion about detecting phone rings on this
>list, I think this question may be appropriate as well.....

> Its collecotor attaches to a resistor which
>in turn is connected to a signal on the Mac ADB bus called PowerOn. If the
>optocoupler operates, PowerOn will be pulled to ground, and the Mac will be
>powered on.
>Now the problem is that I don't want this to happen if the Mac already
>runs. In that case also a 5V signal is available which can be used for this
>purpose. Mark this, the 5 volt signal is not available when the Mac is
>turned off.
>I can't think of anything that keeps the optocoupler from pulling PowerOn
>to ground. Who can help me out?

Some opto's have the transistor base bought out to a pin (4N26 for instance
outputs the base to pin 6)
Could you use the 5V present through another transistor to short this base
when the 5V is present, thus
disabling the opto?
Just a thought...
Cheers,
Kenneth
I don't mind dying, I just don't want to be there when it happens...