This oscillator with emitter follower was found in an American documentation from the 80's. The circuit generates 100 MHz signals and the transistors admit modern equivalents.
This circuit with an industrial standard 4-20 mA interface uses a KPZ20G pressure sensor but can...
This simple receiver with germanium transistor and listening on a crystal phone was discovered in a...
This circuit is from Motorola technical documentation from the 70s, but it can be easily assembled...