| 250 / | HD | RADIANT ENERGY |
| 200 | DF | PHOTOCELLS; CIRCUITS AND APPARATUS {11} |
| 206 | DF | .~ Photocell controlled circuit {9} |
| 214 R | DF | .~.~ Special photocell or electron tube circuits {15} |
| 214 A | ![]() | .~.~.~ Amplifier type {1} |
| 214 LA | DF | .~.~.~.~> Light amplifier type {2} |