Light biassed camera tube arrangements

摘要

The invention relates to light biassed camera tube arrangements of the kind in which the light bias source within the overall outline of the tube envelope has one terminal connected to a heater pin in order to provide a source of power. The other terminal of the light bias source is connected to a lead extending to a terminal carried by a protecive end base cap for the tube and a removable disc is provided to fit between the base of the tube and a valve base into which the tube is plugged, the removable disc bearing circuitry and terminals provided to contact selected ones of the terminals carried by the protective end base cap so that the nature of the light bias provided may be selected.