C135 Off-field School How Can Heartless and Ignorant(2)

"You should understand that this is a very simple thing …" He bent down once again and picked up a mechanical part from inside the wooden house. "This is an optoelectronic semiconductor light-emitting diode, a semiconductor device with unidirectional conductance. In the circuit …"

"Oh, I understand …" I didn't know what to answer.

"It's not a rectifier in the circuit