Found in a 70’s documentation, this circuit can operate with signals up to 10 MHz. The operational can be a modern equivalent.
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...