Right just had to go and save the world with my pants on outside my trousers ,thanks to Chris for sorting out my piccy,the output is ica pin 1 as stated,and it is better than a simple photo diode because the feedback section reduces the effect of a constant dc voltage overloading the receiver,The transmitter can be a simple circuit which just modulates the light emitting diode fully on or off,I found that two ir leds work well over a distance of about 100 feet driven from a 100ma 5volt supply.