This circuit protects the speaker from dangerous direct currents that could damage it. The circuit is from an Electronics Experimenter Handbook 1993 edition.
The frequency of this Pierce oscillator, found in 1969 documentation, depends on the crystal. The...
We found this Nicad cell charging circuit in an English publication from the 1970s. The circuit can...
In the figure we have a constant current source for Shape Memory Alloy in wires or Alloy with...