The examine if open instruction ________.
A) Is an input instruction only used for field devices with NC contacts
B) Can only be assigned an input file address starting I:
C) Has the following logic symbol (- -)
D) Has the following logic symbol (-/-)
Question 2
The light source of a photoelectric sensor used in a long distance sensing application is ________.
A) An incandescent lamp B) A light emitting diode
C) A photo cell D) A laser