SpudFiles

Thanks very much for the explanations. I was wanting to try to build the one with IR LEDs to the MIC input, and just trying to figure out the differences between the two different circuits. Your explanation has answered my questions for sure. Thanks again.

This may be a dumb question, but why does Jim's circuit run only on the power from the mic jack, but this one needs the 3v battery? Is it to give extra power due to the IR LEDs or because of something else?

Thanks!