Not necessary, you can just take an additional CRT and wire it in parallel to one of the Williams tube CRTs to see what's on the screen. That's how the Manches

Not necessary, you can just take an additional CRT and wire it in parallel to one of the Williams tube CRTs to see what's on the screen. That's how the Manchester Baby did it (visible in the center of the image here): https://upload.wikimedia.org/wikipedia/commons/6/6f/Manchester_Baby_Replica.webp https://upload.wikimedia.org/wikipedia/commons/6/6f/Manchest...