Mullard ‘How it Works’ series
This was a series of pamphlets issued by the Mullard valve company in the 1960s, which explained in simple terms err... how it works. The ‘it’ in this case was the domestic radio and TV of that era (note that modern, digital TV and radio don’t work like this), and the pamphlets also described the inner workings of the valves and transistors that made radio and TV possible.
There should be six of these pamphlets altogether, of which I have five. I don’t even know what the missing one (Number 4) was about, but if anyone has a copy I can stick up here to complete the set, I’d be very grateful.
Repair and Restoration of Valve Audio and Radio