We found this configuration in a 1990 Poptronics. The circuit can be powered by voltages between 6 and 15 V, changing the resistors in series with the LED. The frequency is set at R7.
This 1 kHz oscillator has enough power to directly drive a small speaker. The supply voltage is 5...
Obtained in an English documentation from 1977, this transistor amplifier for small signals uses...
This simple signal injector was found in a Radio Electronics from July 1959. The transistors are...