Abstract: An ultrasonic waveguide provides the encoding of magnetic keys on a keyboard. The magnetic keys couple their respective magnetic fields to an ultrasonic waveguide producing signals in a given time relation to permit encoding by depressed keys. Since the necessary information appears essentially on two wires, the system is basically a very reliable solid state system where all basic signal processing takes place in an "integral" ultrasonic waveguide component. Potential simplicity, low cost construction, very high reliability, makes the application very suitable in keyboards for computers, data processing equipment, teletype equipment, computer time sharing stations, computerized reservation stations, display consoles, etc.