This circuit with RIAA equalization is from 1985 US documentation. The circuit has a flat response of 150 Hz to 40 kHz. The power supply must be symmetrical.
This 2009 circuit is a bilateral call warning. Easy to build, using light communication between two...
The oscillator illustrated in the figure can be used to generate signals ranging from 100 kHz to a...
This circuit was used to reinforce radio signals for listening on the phone, making it possible to listen...