Found in a 1967 Electronics World, this preamplifier uses an integrated circuit from that time, difficult to obtain today. The maximum frequency is 15 kHz.
This circuit can be used as a source of signals for generators of different types, sirens, or...
This circuit is based on a 5 V LED flasher. We found it in October 1980 Radio Electronics...
This interesting circuit in which the LED display is circular imitating a common clock appeared in the...