SouthPark and I have been discussing this a little...
Seems the Western Union did most of that kind of "modernizing"
in the late teens-early '20's during line rebuilds and upgrades.
Probably went on for a decade or two before largely completed all over.
The "birdhouse" cable box was placed high above the top arm and the bridle wires were run from the breakirons up into it thru insulated bushings in the sides. They then connected to the Depot cable at a terminal block mounted in the box. Fuses and arrestors were not mounted in the pole-top depot cable boxes...those were placed inside at the switchboard.
The birdhouses eliminated the obvious easy path for lightning to enter the depot buildings that existed with the open wire downleads to building mounted "crossarm and pin" entrances.
Metal Cabinet style switchboards, either the "Single unit" type with carbon protectors, line and instrument fuses for each wire or larger cabinets with carbon block arrestors inside and pin jacks used with patchcords were also being installed during this period, and replaced the earlier peg-strap wooden switchboards.