Eastern Railroad Discussion > Pole lines

There are a number of locations where a pole line follows the railroad. It should be common knowledge that these originally were telegraph wires. Nowadys, some pole lines and wires are decrepit and obviously not used, but in other places it appears that the wires are in good shape. Are these used for anything these days. Just curious.

Signaling. Crossings etc.

On some MOW track diagrams I have seen there is a "Pole Line Legend" that shows what each line wire was designated for. Active Lineside wires are mostly a thing of the past but it would be risky to assume that if, it is still in place, that there is no current being carried. Some wires carried power for crossing installations etc, even 440 volt a.c.. Signal Code Line, and several lines designated for telephone(Block Line, Dispatcher Line, Message Line, Track Supervisor, maybe a line that ties into a public phone access, Yardmaster Line, and others). There would also likely be extra lines, which usage would be assigned by a "Wire Chief" in the case of a wire break or defect.

You may notice on some trackside lines "crossovers" where the line on the north side

changes place with the line on the south side. Typically, these lines are about 6" apart.

These were for teletype circuits.

Be Well,

Tim Colbert K3HX

Um...crossovers (a set of four small insulators on a bracket allowing the wires to swap positions) are more than likely a good bet that that wire pair is carrying a voice circuit. I suppose they could be on telegraph circuits however the point is to reduce crosstalk and it seems unlikely a simple baseband telegraph circuit would suffer from that. Maybe if they're using some sort of carrier system to put multiple circuits on one wire pair. But I'd wager you're looking at a voice circuit.

On telephone cables the two wires forming a pair are also twisted together and nearby pairs are twisted at different intervals all in the name of reducing crosstalk. Open wire lines may seem primitive but they can carry a voice signal a lot farther without amplification than wire pairs in a cable.

Good point about the carrier and voice operation.

The crossovers would serve to improve the operation of a carrier (baseband) multiplex

system.


However, the reason for the crossovers is to prevent the make-break signals from

"smearing" due to a combination of inductive and capacitive coupling along the line

This was an early (1880's) solution to problems posed by multiplexed telegraphy

with multiple stations sharing one pair of wires with messages going both ways.

The make-break frequency for teletype is is much faster than ordinary telegraphy.

Also, the crossovers help reduce the effects of common mode distortion and to a lesser

extent differential mode distortion. The crossovers also tend to reduce (but not

very much) interfering signals from other systems which may be unbalanced and thus

radiate slightly. These effects are very small but when you are running hundreds of

miles of line with conductors (rails, other signal lines, etc) in proximity, these

effects add up.


These problems (mainly crosstalk) are greatly magnified in twisted pair cables due to the

much greater capacitive coupling. And, when the cable gets wet...big trouble!


Teletype signaling was one of the things covered by my specialty whilst in the

service. "Landline" signalling for voice, control and teletype; a mixture of "direct"

and carrier multiplexed systems (some of it with 75-90 year old DCC insulated under-

ground cable, some "overhead" lines) was part of my job for about 26 years.


Be Well,

Tim Colbert K3HX