This circuit was found in old American documentation. It has 40 dB gain between 10 Hz and 10 kHz. Modern equivalent transistors can be used.
This traditional flasher configuration with two transistors drives 5 LEDs with a supply that must...
To operate with high input voltages using a 3-terminal voltage regulator such as the LM340-15, we...
This is the circuit of the commercial Japanese megaphone of the 60s model DM-218. The circuit uses...