An above ground set of electric lines for the transmission of
power, data and communications. Based on an N&W prototype, this kind of
construct could exist wherever an electrical transmission system is operated.
By the summer of 1956, Norfolk & Western carried all of its power, signaling and
communications' wires on a single set of electric line poles paralleling their
trackside right of way (ROW).
The general arrangement of the electric lines and poles is as follows:
At the top of each pole, a pair of non-insulated ground lines connects the
lightning arrestor.
The upper crossbar carries just two non-insulated copper lines. These were
the N&W's own 3-phase 4800V 60Hz AC power buss and its associated ground line.
This power source ran everything from the signals and electro-pneumatic switch
motors, to the switch point heaters and the lights in the stations along the
ROW.
The middle crossbar also carried a single pair of insulated lines. These were
the signal lines used by N&W to affect Centralized Traffic Control (CTC) over
its mainline signals and switches. The signals were issued and confirmed via
encoded sequences of sixteen long and short data pulses. The first 8 coded
pulses identified the receiving station, signal, switch or monitoring system.
The last 8 coded pulses carried the specific command or update code.
No doubt the N&W techies thought this was a sophisticated variant of morse code
from the old telegraph days... Little did they know in 1956, that the CTC
signaling system represented a crude form of binary machine language.
The lower crossbar carried varying numbers of insulated twisted-pair
communications wires. The communications lines had been carried on separate
Western Union poles on the opposite side of the ROW from N&W's own poles until
1955, when WU announced they would be abandoning their trackside support of
railroads.
In order to avoid having to maintain two sets of poles and lines along their ROW,
N&W borrowed a relatively obscure technique for handling communications line that
were to be colocated on the same set of poles as high power lines. The technique
would later come to be known as 'twisted pair' - a term familiar to modern day
networking techies.
At periodic intervals the communications line pairs were physically reversed via
special brackets attached to the crossbars, so that interference from the high
power line on one of the comm lines would be neutralized as the same inteference
was allowed to affect the other line for a similar distance.
Тип: track