Cadmium sulfide

Lead selenide

Zinc sulfide

Copper sulfide

0.1MA to 1.2MA

0.2MA to 1.6MA

0.3MA to 2.7MA

0.4MA to 3.8MA

Uni - Junction transistor

NPN - Photo transistor

PNP - Photo transistor

Audio frequency transistor

Amplifier the signal

Converts voltage into current

Produces electrical noise signal

Defects the operation of switching signal

0.5 V

0.8 V

2 V

2.5 V