(under subclass 15) Subject matter including a casing or covering such as a glass or quartz envelope containing the photoconductive element, at least a portion of the casing or covering freely passing the radiant energy which impinges on the photoconductive element.
SEE OR SEARCH THIS CLASS, SUBCLASS:
184, and 199, for mechanically variable resistors with housings.
226+, for incased, embedded, or housed resistors generally; and especially subclasses 234+, for such resistors with gaseous or vacuum spacing between the element and the casing or housing.
