> A static gap only > fires twice per mains cycle, 100 times for 50Hz (UK) 120 times for 60Hz (US) Depending on the gap spacing, you can get multiple gap firings from a static gap. My small coil under loow power with just a few gaps in series can give me 3 or 4 firings per half cycle. Rotary gaps come into their own with high power systems where quenching of a regular static gap would be difficult or impossible. Steve Roys.