I wish to build the Arduino ultrasonic receiver circuit in the attached photo. The circuit is in the book Arduino Circuits & Projects Guide (http://www.amazon.com/gp/product/1907920250?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s03). The author recommend your site to purchase the components for the circuit (the author dose not provide a list of components). I do not recognize items 1 & 2 in the circuit nor can I associate them with the schematic.
Please tell me items 1 & 2 are in the circuit.