This is a simple tubed mixer from the 50's. The circuit does not include the power supply and has 3 inputs with independent controls. The tubes are double and the inputs are high impedance.
One 40108 Schmitt inverter or one 4093 gate can be used as a half monostable to be triggered by...
This signal generator found in Japanese documentation of 1973 uses an unusual integrated circuit...
This is the basic configuration of an operational amplifier as a current regulator. We found it in...