The TMA406 is a scan converter storage tube with two electron guns, one for writing the image and the other for reading the image. Both guns are electro-statically focused and magnetically deflected. The independent scanning systems and the central storage of the image allow for the scan conversion.
The primary aim was in Radar systems where the main plan position indicator (PPI) display with the rotating display could be converted to a standard TV raster for display on auxiliary monitors.
Additionally the tube could be used for extracting a slow-scan image from a fast-scan original. There is no information as to whether it could be used for TV standards conversion. For example from the 525 line American standard to 625 lines in Europe. I remember seeing the Rowan and Martin laugh-in in the late 1960s in a small rectangle on the TV screen as that was the best standards conversion available at the time.
The maker's label, B9D base pins and writing gun.
The electrodes of the writing gun are held in position within glass rods.
The reading gun and B9D base. Both guns have evacuation pips.
A closer view of the electron lens in the reading gun.
The central target assembly with a glass diameter of 79 mm. On the right is the EHT connection for the writing gun. On the left are the signal extraction rings.
The central 'screen' is seen as a white disc.
The wide glass tube envelope is 36 mm in diameter and, excluding the two sets of B9D base pins, is 590 mm tall.
Reference: Data-sheet. Type TMA406 was first introduced in 1970.