Signal generator (CB21057E)

Found in Popular Electronics, this '90s circuit generates harmonic-rich signals for testing audio equipment.

12 V Battery Charger (CB17546E)
This type of circuit and with this integrated circuit appears several times on this website. The...
Crystal Controlled Multivibrator (CB23783E)
Using transistors of the time, this circuit was published in Radio Electronics magazine in...
Integrated AM Radio (CB18179E)
The integrated circuit used in this 1982 project is not very common today. It can be adapted to...