Why would Western Electric choose a Tungar rectifier?
This was the pre-silicon/germanium era. Tungars could provide a wide amperage range
of cheap rectifiers. Simple to replace regularly. ( Bell switch men were in phone
exchanges continuously.)
Once my sister got me a Christmas job at a department store with PBX that used
Tungar rectifiers.
I fished an old one from the trash bin when I went to get a trolley load of stock
for the drug store department. And the 'floor walker' almost skinned me alive.
