[GreenKeys] Polar Loop wiring?

[jhhaynes at earthlink.net]

If there is more than one sending machine then you don't have a polar
loop.  A polar loop works fine where there is one sending machine and
lots of receive-only sets - you just wire them all in series.  But
when there is more than one sending machine it gets complicated.

Don and others can tell us more about it, but I believe what is done
in the business is to make a virtual loop - it behaves as if all the
machines are in series, but it doesn't really work that way.

One thought is to have two physical loops.  One contains all the
keyboards or senders, and the other contains all the receivers.
Then at one end point the two loops are connected together (or
through a repeater).  You wire the sending loop with relays such
that at each station you either send spacing polarity or you pass
along whatever polarity is coming toward you.  Thus at the end of
the line you will see marking if all of the stations are sending
marking, and spacing if any one of them is sending spacing.
Then you send that polar signal back out through all the receiving
relays.  This is what you might do along a railroad where the
stations are located along the route of the physical line.

I suppose you could do it with a single wire, but then you would have
to have a polar circuit from one station to the next, and a repeater
at each station that would relay the signal incoming on one line to
the outgoing line in tandem.  Then it would allow the local station
to copy signals incoming on either line, and to send to both lines.

More often you have a telegraph company supplying the service and
customers' offices that are connected to the nearest telegraph
offices by local lines.  A local line could be neutral or polar
or might have two wires for separate sending and receiving legs.
At the telegraph office you have a thing called a network entry
repeater or a hub repeater for each customer office served by
that telegraph office, and for the main line that runs between
telegraph offices.  The main line might be a duplexed wire line
or a pair of channels on a voice-frequency carrier system, one
for each direction.  The network entry repeaters in an office are
connected together with what is called a dummy or hub circuit.
The function of the network entry repeaters is that if a space is
received on any of them it is propagated to all - except if
the space came in on a neutral loop it must not be propagated
back out to that loop, lest the whole circuit be locked up spacing.


jhhaynes at earthlink dot net


On Tue, 15 May 2007, Brooke Clarke wrote:

> Hi:
>
> In a conventional Neutral loop you can just wire a series of machines all in 
> series.  The idle machines look like shorts and pass the loop current.  When 
> any machine sends all the others see the signal.
>
> But how do you wire a Polar loop?
>
> -- 
> Have Fun,
>
> Brooke Clarke, N6GCE
> http://www.PRC68.com
> http://www.precisionclock.com
>
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