This simple clock can be used to generate signals up to 100 kHz, depending on the crystal. We found it in a 1967 documentation. Note the high supply voltage.
This simple photometer uses a 1 mA milliammeter and a common phototransistor. The circuit has its...
The circuit of the figure allows to implement a multimeter of high sensitivity or even to use a...
This simple circuit must be powered by a voltage of 5 V. The integrated circuit is the 7400, but...