trainsinmaine wrote:Back in the days of railroad telegraphy, did the number of insulators and wires on telegraph poles directly correspond to the number of telegraph stations (depots) on that particular rail line?
I recall the question about lineside wires being asked during an elementary school field trip to the local B&O station in mid-1950’s. (A classmate’s father happened to be the agent/operator there....). As I recall it was explained to us like this:
A railroad’s phone or telegraph system is essentially a “party line”. A single pair of wires provides service to every station along the branch or section.
Another pair of wires brings public utility electric (120 VAC I presume) from the nearest highway crossing to the battery chargers in wayside signals, grade crossing signals, powered switches, etc. (Incidentally us kids were admonished to stay away from the wires on account of the electrocution hazard presented by the power circuit!)
The remainder of the wires are dedicated to wayside signals, etc. I presume by this it also includes remote switch operation, automatic train stop control, probably a 2nd phone line or utility power supply, possibly a few unused spares, etc.
Obviously the more control functions a particular line had the more lineside wires were necessary, thus accounting for this observation:
On the single-tracked B&O my class visited the poles had 3 crossarms and carried about 20 wires altogether. (The line was ABS signaled at the time).
The PRR branch at the other end of the village - a very sparsely used, unsignalled branchline - had lineside poles with single crossarms supporting a meager 4 wires. I surmise now these were simple phone and/or telegraph circuits.
OTOH on the nearby 4-track NYC main (heavily used and fully-signaled) the poles carried 5 - 6 crossarms with a dozen or so wires on each – probably 70 wires altogether. Had to have been a nightmare for signalmen in wind and ice storms…
dummy wrote:are glass insulators still being made? or are they using plastic now?
I doubt it. Lineside wires are rapidly disappearing, replaced by buried cables or fiber optics. Ie. the pin-type glass insulator in railroad service is going the way of the steam locomotive.
Also when the Conrail Westshore branch lineside poles and wiring were replaced in the late 80's the new insulators were of a tough, engineering grade clear plastic - lexan perhaps? Now 20 years later scattered amongst the the clear plastics are newer, black "pony" sized insulators. These are made of a rubber compound that looks/feels very much like tire rubber. I expect these are about as bullet-proof as an insulator can get.