Found in a 70s RCA manual, this circuit uses transistors from the era. Equivalent types can be used such as TIP31 for Q1 and BD135 for Q2.
Other series amplifiers such as the MC3301, MC3401 and LM2900 can be used on this circuit. We...
This configuration, widely used in our articles and on this website, uses a 555 to control a relay...
This circuit was found in an English documentation from the 90s. It uses a PLL CMOS 4046 and is...