That mast arm reminds me of a similar mast arm in Spokane, I think it's the oldest signal in the city (W Broadway & N Lincoln):
https://goo.gl/maps/qmLzadsDa1xBNaQ68
I think they are called double-guy or something? I always thought they were neat.
Wow, there are a bunch of "double guys" associated with that particular intersection. Indeed, the mast arms are attached with "double guys", but there are also two sets of signal wires crossing North Lincoln Street and we call those "double guys" as well. The term "guy wire" is a nautical term adopted by railroads and their telegraph partners during the advent of telegraphy and electrified signalling. The term refers to the use of cables to support "riggings". So technically, the aerial support of a cable span is not a "rigging" and the only reason we call them "guy wires" is that we originally used the same type of cable as the "down guys" (guy wires used to either back-brace the pole to the ground, or in your case, guy wires used as true riggings to support a side mast).
There are actually six sets of "double guys" at this location: four "double guy" signal mast arms, another for signal wires crossing North Lincoln Street shown here, and another on the right crossing West Broadway. But one of those "guy wires" isn't supporting anything. If you look carefully, it is the newer of the two guy wires crossing the street (you can tell because it is self-supporting cable where the jacketed cable is twisted along with the guy wire). (If I want to get technical here, the set crossing North Lincoln Street is actually a "triple guy" with a little flimsy self-supporting cable hanging just a few inches under the top one and not supported by the top one).