We found this circuit in a 1965 Electronic Design. Transistors are still common but admit equivalents for some of them. The circuit drains a current of only 4 mA.
The circuit shown below is from the National Semiconductor's 1994 Linear Applications Handbook. The...
This metronome was found in a 1979 publication, but it can be assembled more easily with the BC548...
This circuit for a maximum current of 1 A is the most common version that uses the 78 and 7905...