The head of the pole needs to provide a freely rotating hub, and usually incorporates a ball bearing race of some kind.
In addition, where signals and power need to pass to the model, some form of slip ring arrangement is required.
The use of electric power can permit sophisticated control effects such as retracting undercarriage, operating flaps, etc.
However the limited degree of freedom of the tethered model precludes the use of full aerodynamic control.
The control console can be nothing more than a simple rheostat allowing the current supplied to the model to be varied.
Typical RTP set-ups allow multiple models to fly simultaneously on the same pole.