This circuit is from American documentation from the 1980s. The transistors are general purpose types and the relay can be 6 or 12 V depending on the supply voltage.
This stage was found in a 1964 Electronic Design. The transistors are of the time and the shape of...
This circuit with the known PLL 567 can be found in other versions in this section and in this...
In this circuit, the LED Will blink in a presence of na áudio signal in the input. Gain is...