A rotary gap is a motor driven gap that has a solid disk with
electrodes mounted around its periphery. These electrodes come
into line with stationary electrodes to form the gap. As the
disk rotates each set of electrodes comes into play in sucession.
With a large number of spinning electrodes and a high rotational speed
the number of gap presentations can become quite high. And quenching
is quite good with a rotary as the electrodes are in firing position for
only a short time.
Rotary gaps work well with higher power systems but are unnecessary with
small to medium power systems running from neon sign transformers.
In fact neons work better with one of the multiple static gap systems and
can actually be damaged by a rotary gap.