This circuit was found in an English publication from 1967. The circuit is for listening on a phone. Transistors are types of germanium of the time.
This page shows a crystal oscillator for 2 MHz. Other frequencies can be produced depending on the...
This circuit is from a 1970 publication. The time constant is given by 1.3R x C where R is the...
The supply voltage range of this circuit ranges from 4 to 20 V and the power depends on the chosen...