Found in an Electronics Now from the 90s this mixer has several inputs. The integrated circuit can still be found easy and the power supply need not be symmetrical.
Ordinary batteries cannot be recharged, but they can go through a process of "rejuvenation" that...
We found this basic circuit of a relaxation oscillator with unijunction transistor in a 1976...
This circuit, from a 2006 documentation, automatically controls the activation of a water pump, and...