These connections were made via "potheads" which were a means of terminating the feeder cables down into a porcelain, oil-filled, insulated coupling whereby the upper cables joined together with the underground conductors that extended down the rest of the pole. Oil was used within these pole-mounted terminations to keep them cool. Large ribbed bushings were also part of these units, insulating the primary voltage.

In this instance (on the lower crossarm) there are two incoming lines connected. They were joined together into a two-conductor cable as you can see (the backside is shown)