This unit is part of the ARI 5874 Airborne H.F. radio communications equipment and was concerned with the Suppressed Aerial Systems.
The control unit Type 7216 has 3 main functions:
It enables the operator to take direct control of the frequency range selection and tuning of the suppressed aerial system.
It is used for setting up the aerial system on preset frequencies
It gives a measure of manual fine tuning after the system has been automatically set up to a frequency channel.