Found in American documentation from the 90s, this circuit can be applied to other operational ones. We found it in an EDN of the time. Next to the diagram is the response curve.
This VCO or Voltage Controlled Oscillator uses common components. TR1 can be a BF245 and TR2 a...
This control for a heating element was found in an old documentation. The current in the element...
By pressing and releasing PB1, only one LED is lit, drawing a number from 1 to 6, as in a die. The...