Hi,

Since there has been some discussion about detecting phone rings on this
list, I think this question may be appropriate as well.
Detecting phone pulses with an optocoupler and a couple of diodes/resitors
and capacitors is not too hard. My problem lies at the other side of the
optocoupler.

________________    -----[100ohm]----- Power.On
optocoupler   __|__/
             /  |
    LED     |   |
             \  |
              --|--
________________|  \ gnd

Ok ASCII art is not my strongest point. What it depcits is the receiving
transistor in the optocoupler. 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?



                                              Ronald