For the question about Early/ old kind of electrical technologies that are no longer available today, or almost extinct.  This includes most kind of Thermoionic valves, gas filled tubes, magnetic tape cassettes and heads, Reel to Reel, CRT, Light pen, Light guns, Analog radios, VCR, Post office box, Telegraph, Electric heaters, Pipe light choke and starters, incandescent bulbs, Punch card readers, Landline telephone, rotary diallers, Meters of various kind based on Magnetic deflection, and every other kind of vintage electrical technologies.