We found this frequency meter circuit in a 1974 documentation. The circuit is powered by 12 V and has 8 digits. Changes can be made using a prescaler to reach higher frequencies.
This traditionally configured power supply provides +12, -12 V and 5 V voltages for operating and...
This simple circuit for headphones or small speakers was found in documentation from the 90s. The...
The operational amplifier used is not common today, but the circuit can be implemented with modern...