I am trying to to create this freq Meter. https://www.arduino.cc/en/Tutorial/SimpleAudioFrequencyMeter
what are these components: The black circle object to on the left of the breadboard. ( I think its the potentiometer) The figure on the bottom, on the separate green board.
Another question involving the schematic: what is the three pin object located at the U1 (sleeve,right,left)thing is what is the
Thank you for your help