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Early Broadcast Equipment

Diamond Power Cameras - Negative Images

When I first got our Diamond Power image dissector camera to produce an image, I discovered that the camera's output was negative - black was at 100% and white at 0. Sync and blanking were normal (not inverted). At first I thought that there might be two versions of the dissector, and that we had the wrong one in the camera, but I soon learned that all the dissectors made by Diamond produced an output where more light resulted in a higher negative voltage out.

This was confusing, but I now think that Diamond used negative images in their camera system that was designed to televise instruments in a furnace environment.

Here is a summary of the Diamond Power image dissector cameras we know about:

Model 100

Early Television This camera was made about 1947. It used a dissector made by Farnsworth. By 1949 the tube was being made by Diamond Power. Nothing is known about whether it produced a negative or positive image, or what monitor it was used with.

Model 300

Early Television


Made about 1949, we have extensive documentation on it. The camera produces a standard video output. The monitor produces a positive video image.
Early Television The monitor produces a positive video image.

Model ? (our camera)

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The camera produces a negative video output with normal sync and blanking. It has a composite video output and a RF output, which is also negative. Since the RF output has negative video modulating it, a negative image would appear on a standard TV set. This tells me that it was designed to also work with a monitor which produced a negative image.
Early Television These monitors produce a negative image with a positive video signal. They are not designed to work with our camera, since they take separate video, horizontal drive and vertical drive inputs, while our camera only has a composite video output. I suspect that Diamond made a similar monitor that took a composite video input. They are model number TI 300-1, indicating that they are the same vintage as the model 300 camera.

George Lemaster has done extensive patent research about Diamond. Here is what he found:

Various designs for boiler water level gauges were patented by Diamond Power Specialty Corporation. In the period 1947 to 1957 dual color gauges were developed which used red and green lamps to illuminate water in a translucent tube. The bi-color gauges helped operators read boiler water levels and discriminate between water in the gauge column and steam, which could obscure the true water level. Mis-reading the water level could lead to catastrophic results.

Bi-Color gauges were developed by Blackburn in the mid-1930’s in the UK, patents 2,024, 815 and 2,115,899, which, use the differences in refraction index of steam and water. In the Blackburn gauge, steam, showed red color while water showed green, using a prismatic gauge assembly.

Patent 2,573,006, by James Good of Diamond Power (filed 1947), developed the Blackburn gauge as a “Telegauge” for remote viewing by television. Good discusses that conventional television equipment using iconoscope or orthicon tubes did not have the ability to satisfactorily distinguish the red and green gauge areas, so the dissector was employed.

In describing the gauge operation by video camera, Good states the dissector responds more strongly to red than green. When used in the Blackburn steam gauge, the steam, or red area on the gauge, appears on the video monitor as a bright area where the green, or water area on the gauge, appears black. This is the type of clear indication operators need in viewing the water level gauge, not a high resolution image of a dial or similar gauge.  Diamond patent 2,949,031 depicts a  water gauge with seven small circular windows, something like that shown in the photo of the Diamond monitor in operation at a power station control room.

It appears the Diamond dissector camera, in this application, does not need the resolution or light sensitivity generally associated with conventional television cameras, and, due to the bi-color application the ‘negative’ video polarity may be the intended design.

All the patents can be viewed at https://www.pat2pdf.org/