terryking228, I'm not using any libraries right now. My immediate goal is to detect an IR beam break. Later that working hardware and code would be incorporated into a final project sketch. I suppose you could say I'm sending and receiving at the same time but not via the Arduino in that the 38khz functions are autonomous in the sending and receiving devices. The sketch enables the sender to send a stream of 38khz pulses for a brief time and checks the receiver's digital output. Perhaps I don't understand what you are asking. - Scotty