Timer for enlargers (CB8301E)

From the time when photographs developed on paper could be enlarged, this circuit was found in a 1960s General Electric documentation.

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Infrared Sensor with the MC3373 (CB4580E)
An interesting option is the one that makes use of the MC3373 integrated circuit and which is...
High voltage source for Geiger counter (CB8478E)
Found in a 90s Popular Electronics, this circuit generates high voltage for radiation detecting...
Adjustable Q Notch Filter (CB15475E)
In the figure we have an interesting configuration that allows, from a double T filter, to change...