Battery Monitor (CB6067E)

This simple circuit has its trigger point set in the trimpot. The transistor can be any general purpose and the LED of any color.

Code Practice Oscillator (CB4207E)
Also suitable for use as a noisy alarm, this Morse Code or telegraph practice oscillator was found...
Varicap Frequency doubler with (CB4107E)
We find this circuit in American documentation from the 1980s. It consists of a frequency folder...
Wide Band Oscillator (CB4932E)
The frequency of this oscillator can be set in a range from 5000 to 1. We found it in an old...