A number of companies were working on various solutions to this problem in the late 1940s, using three separate tubes or a single white-output with colored filters placed in front of it.
[2] The dielectric ensured that stray electrons, either off-voltage from the guns or secondary emission from the phosphors themselves, were stopped before they reached the screen.
The penetron was ideally suited for use with the early CBS broadcast system, which sent color information as three separate sequential frames.
Unlike the mechanical CBS system, the penetron had no moving parts, could be built at any size (which was difficult to do with the disk), and had no problems with flicker.
This meant the high voltage color selection grid had to be rapidly cycled, which presented numerous problems, notably high-frequency noise that filled the interior of the tube and interfered with the receiver electronics.
Another modification was introduced to address this issue, using three separate guns, each fed with a different base voltage tuned to hit one of the layers.
Other developers continued working with the basic system attempting to find ways of solving the high frequency switching issues, but none of these entered commercial production.
This was very useful for radar display and IFF systems, where the images were often overlaid with textual cues that required high resolution to be easily readable.
This was a major advantage in the avionics role where power budgets were often quite limited, yet the displays were often hit with direct sunlight and needed to be very bright.
The lack of the shadow mask also meant the penetron was much more robust mechanically, and didn't suffer from color shifting under g-loads.
Better focusing allowed the size of the holes in the shadow mask to increase in proportion to the opaque area, which improved display brightness.
Problems with doming were addressed through the use of invar shadow masks that were mechanically robust and attached to the tube using a strong metal frame.
[6] The main advantage to the penetron is that it lacks the mechanical focusing system of a shadow mask television, which means that all of the beam energy reaches the screen.
This is a major advantage in an aircraft setting, where power supply is limited but the displays need to be bright enough to be easily read even when directly lit by sunlight.
The system is guaranteed to produce the correct colors in spite of external interference or the g-forces of maneuvering – a very important quality in aviation settings.
The penetron also offered higher resolutions because the phosphor was continuous, as opposed to the small spots in a shadow mask system.
Sinclair experimented with a variant of this technology on his early pocket TV screens, but was unable to produce an RGB version.