This traditional circuit generates a 200 Hz sinusoidal signal. The frequency depends on the capacitors and the transistor can be a BC548. We found this circuit in a 1979 documentation.
This small general purpose and RF transistor tester appeared in a February 1958 Radio Electronics...
The MC4741 integrated circuit consists of four operational amplifiers similar to the 741 in a...
We found this touch control on a Popular Electronics from 1970. The circuit makes use of an...