OptoIsolated Devices & power supply

I have been playing with some different OptoIsolated components (OptoTransistor, OptoTriac) as a way of providing isolation between the trigger section, and the output section of some different circuits, but it seems that 2 separate power supplies would be needed to truly keep the sections isolated. Is this indeed the case, or is there a way that one power supply (battery or plug-in) be used and still allow full isolation?

Well technically you need two power supplies anyway.

You could use a pulse transformer to trigger a triac but you still need anther power supply (the voltage you're switching).

You can buy high quality expensive regulated isolated power supplies or make you're own unregulated isolated power from a transformer.

Hero999 - Thanks, when I was drawing the circuit, and using a 9 volt battery for the trigger side, I sort of thought this was the case in needing a separate battery for each output side if I wanted to maintain true isolation.

Michael