The heavier cables on the left provided 600 volts DC to operate the trolley system here and throughout the rest of the system in Boston. The poles were steel and employed some pretty hefty crossarms with heavy-duty steel braces supporting them. I am unsure what kinds of insulators originally were upon these lines. At some time (perhaps during the original line installation?) a lot of bakelike side-tie insulators were used. Many of these poles still are standing in service; the majority having standard light gray porcelain saddle groove insulators supporting the DC cables.

The lines on the right were for telephone or electric customers.