Sit directly face-on with a portable keyboard at a height where your arms are straight out in front of you.

A minicomputer controls the radar and processes the signals and the operator can communicate with the system through a portable keyboard terminal.

These instruments can be considered the predecessor to modern portable keyboards, as they included one-touch chords, rhythm and accompaniment devices, and other electronically assisted gadgets.

While a few such instruments are still sold today, their popularity has waned greatly, and many of their functions have been incorporated into more modern and inexpensive portable keyboards.