NK Tower. I can imagine that traffic was running heavy in one direction for the morning inbound commuters and just the opposite for the evening outbound running. It would be great to hear from former Train Dispatchers as to how often those sets of crossovers were used for flexibility during those commuter rushes in both directions.
I know we lost FH tower to a fire in 1960 or 61 and DV Tower took over the board after. Speaking of FH Tower. It seems funny that all of the other towers had been rebuilt in the 1920-30 time frame from wooden towers to the brick standard for the Electric Division except FH which remained a wooden tower.
It think NK tower was a singular case. I’ve made several thousand trips through that interlocking and can’t recall ever changing tracks.except when they were doing constructionat 125th Street. Prior to the 125th St rebuild, the tower seemed to exist solely for handling two kinds of exceptional cases.
For completely normal operations there was no need for the tower. The distance between the home signals at U (59th ST.) and MO (140th St) was close to exactly three miles. NK, about 100th St., was exactly in the middle. It was needed only for exception conditions, which included
– limiting out of service distance for track maintenace
– bypassing breakdowns
– reducing delay from construction projectsd.
Could that be said of any other tower in the U.S. ?
I have no knowledge of what has been done to the power transmission
system since even PC days. I left before the PC merger.
The duct runs may well be the same, but cables may have been replaced.
Proper maintenance includes repeat Meggering of the cable insulation and
keeping a record of the values obtained, which aids in predicting future
problems (failures) with the cable.
Given the redundancy available, there should not have been any
scheduling problems in getting a circuit shut down for testing, and it
would have been non-invasive, working from the breakers as access points.
Ultimately insulation degrades, and, FWIW, rats like the taste of lead
sheathing, so can do their own damage.
And, underground lines and manholes may be assumed to be wet, if not
flooded.
It would not surprise me if cables were not replaced occasionally.
I was not aware of the loss of the wayside transmission towers.
When you describe the power transmission lines on the steel towers,
please include the underground duct lines that carried more power circuits.
I was only indirectly involved with these, but as I recall, at least on
the Hudson Division, there were two pole circuits and two duct circuits.
Each substation tapped in one tower circuit and one duct circuit, which
ran in and went through circuit breakers to the sub. There were also
circuit breakers outside the station that could be closed to bypass a
substation and were not affected by events inside the sub.
This redundancy provided a high degree of reliability.
If the overhead lines went down (as down on the ground) the duct lines
carried the power. Same for the duct lines, backing up the tower lines.
Two duct circuits were never together in the same manhole, so a failure,
such as fire or explosion in a man hole, would not affect the other circuit.
PenneyVanderbilt 
Reblogged this on John Cowgill's Literature Site.
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