Obtained from a 1969 documentation, this circuit can operate at frequencies up to 500 Hz, counting up to 999. The circuit makes use of neon lamps of the time.
This 1965 Philips circuit uses old company transistors like the BFY51 and BFY50. The circuit is...
This circuit generates the sound of bells. We found it in a 1977 Radio Shack publication. The...
In the figure we have the way to connect solar cells in series in order to increase their voltage. The...