About: http://webisa.webdatacommons.org/105182723

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	So when the Arduino sets a pin high, it turns on the LED in the opto-coupler, which in turn turns on the photo-sensor, which completes the circuit.Here is a picture of my telegraph key shutter release to give you an idea of the setup.
http://www.w3.org/ns/prov#wasQuotedFrom	arduino.cc