Quote Originally Posted by Jack Dahlgren View Post
Q1 in the schematic is the phototransistor. It is denoted with the three slashes to the left of it. I'd guess that you would get close to your supply voltage out of the circuit, but you can test it.
Thanks Jack, but I'm puzzled because the types suggested for Q1 are all small signal transistors of the type used in amplifiers and other circuits - I can't see how they can function as light-sensitive devices. I'm obviously missing something here, as it appears from other posts that the circuit works. If anyone can put me straight on this I'd be very happy.

Thanks,

Barry