The transistor used in this circuit is uncommon today. AC124 or equivalent such as AC188K and 2N2431 can be used. The circuit is from the 80's and makes use of transformers.
) This interesting circuit of 18 multiplexed LEDs was found in the February 1992 issue of Radio...
This 1969 Philips documentation circuit makes it possible to control an engine through the sound...
This circuit can operate with 5 uV to 1 mV input signals from low impedance sources such as...