Contains extra capacitors to increase the total watt/seconds available. Boosters only effect the highest setting on a power pack. While Boosters require a power pack to run from a battery, Control Boosters will run by themselves on an LU058 Series AC Power Supplies. Over 800 w/s through one head requires a 2400 w/s Quartz flashtube.
Three position switch to send boost up or use 100 w/s or 200 w/s from its own head jack (both turn boost off).
Now stackable up to 2400 w/s, since 1997.
When you double the w/s you gain one f-stop (200 w/s to 400 w/s or 800 w/s to 1600 w/s) and get half as many flashes per charge.
Extra head jack can be used (as-) symmetrically in conjunction with the power pack and other Boosters.