Re: Ever Ready Torch
I once used one of those lamps for a sort of fibre-less fiber-optic link for a school open day when I was doing my A-levels. Must have been in the late 1960s.
The transmitter was one of those lamps with the top removed and the output of a valve amp clipped between the top battery contact and the lamp casing. The bulb (via the battery) provided the load on the amp, and the secondary of the output transformer provided the DC path for the lamp "bias". The receiver was based on an OC71 with the paint scraped off (much cheaper then an OCP71) with a 3" lens in front of it. The setup worked down the length of the blacked out physics lab (other folk had other optical demos involving prisms, etc) - probably 30 feet or so.
Programme material was provided by a reel-to-reel tape recorder at one end played via the optical link to the speaker at the other end. It worked best with the modulation set to hardly cause a visible flicker to the bulb brightness. Parents were duly impressed that they could affect the audio by moving their hand through the beam, but I don't think it could have been called "hi-tech" even in the 1960s!
S
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