This amplifier for hearing aid was found in a 1968 documentation using an integrated of the time. The power is from a battery, the consumption of 1.65 mA and the power of about to 1 mW.
This converter for the 150 MHz band was found in an American documentation. Transistors are...
This 3-component circuit uses an analog indicator. We found it in an old publication....
This circuit is used to detect the water level in a reservoir. It triggers the charge when the...