The HS256 is a colour camera pick-up tube designed for CCTV applications and this example came from a camera used to observe corridors in a block of flats.
These camera tubes are all based on the principle of external magnetic scanning of a low velocity electron beam across the target. The lens system would project the subject onto the target window in the same way that a camera would form an image in the plane of the recording film.
The circuit board was originally fitted with wires coloured red, green and blue for the colour signals to the amplifiers.
The 7 pin base and gun assembly. The heater connections can be seen in the centre right of the picture.
The complexity of the target end is clear, the meaning of each of the structures is not.
The thin glass tube envelope is 18 mm in diameter, and excluding the base pins is 103 mm tall. The target end is 28.5 mm in diameter and the light sensitive area is 13 x 10 mm.
Updated June 21, 2013.