[GreenKeys] polar loops

[kf9nz at juno.com]

      Time for a little nostalgia here.   When I started as a
communications maintainer on the ol' B&O about a half century ago, we
still had a morse circuit and a teleprinter circuit running from GC
(Grand Central Station - Chicago that is) to  Garrett Indiana on open
wire.  They used polar circuits with panels we called "red button duplex"
 (all the knobs and buttons were red).  They were the biggest pains in
the rear!   The advent of the herein mentioned sealed merc wetted polar
relays solved a lot of the troubles - just about the time we abandoned
the morse circuit and changed the printer circuit over to Lenkurt 22A
speech plus duplex which rode a C carrier channel  (3 KHz  Freq. Division
Multiplex).   We used to get a lot of stuff crammed on to one open wire
circuit!    Only problem was, when that one circuit went in trouble -
ouch!
        Then they stopped cutting trees and brush along the track,  the
price of copper went way up and copper thieves drove us crazy. The whole
open wire pole line was junked, lots of linemen lost their jobs, and when
I left we had our own fiber optic and microwave network   We had more fun
balancing the polar circuits and trying to adjust 255A polar relays.
        I just remembered something about adjusting polar relays!  
Somebody on the RR built a gadget to adjust theses relays.  It had a
square wave generator of some kind that pulsed the relay, and a zero
center milliammeter on the contacts.  The idea was to adjust the magnetic
bias and contact spacing on the relay to keep the needle on center.  It
was a "home built" device, but  I think it was based on  a commercial
unit.

Frankf9nz

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