Betwween 1960-80's the most popular strobe power pack for portraiture photography was the Photogenic Flashmaster AA01. It had asymmetrical qualities that would allow the photographer to have four light heads with varying amounts of light output be merely changing the program plug. There were 41 different program plugs that could give the photographer 41 different combinations of light output. There were even program plugs that would make the unit completely symmetrical the same power to all light heads and these units had voltage regulation consistent output. 400 watt/seconds was adequate for "head & shoulders".
School photographers used these units by the thousands and it was the favorite of many studio portrait photographers. Although this model is no longer manufactured, it still is the only entry level power pack ever made that could be completely asymmetrical or completely symmetrical, or a combination of the two by merely changing the program plugs.
The #4 program plug features a power distribution of 400-200-50-50