Re: Repeaters

John....

A Morse telegraph "automatic" repeater (there were numerous designs over the years, some highly successful, some not so good) was used on extremely long lines to overcome leakage losses, or, perhaps more frequently, to provide a "branch circuit" to an existing line where required.

(read "The Modern Practice of the Electric Telegraph" by Franklin L. Pope for info on many repeater designs)

The basic operating premise of any repeater was to "repeat" telegraph signals from one wire to another, while "holding" the opposite line relay "closed" so the wire being repeated to could "break" or interrupt the sender and then send in the opposite direction. Operation was symmetric in either direction.

Repeaters generally required a source of both mainline and local battery, and consisted of two to four specialized relays plus other equipment that had to be kept in proper adjustment for weather-caused line condition variances.
This required trained personnel at the repeater site to maintain them properly.

Due to the fact that a Morse telegraph circuit is (and has to be) basically a simple series DC circuit, it is not possible to just attach a "branch" wire to the main wire at some intermediate point and expect it to work correctly.

So, in order to provide service on a branch line, the only two ways to do it were to either "loop" the main wire physically up the branch, and keep it insulated from ground at all points, or to use a repeater at the branching junction point, with it's attendant required personnel, equipment and battery supply.

For shorter branches, especially the ones out in the sticks, it was far more economical and simpler to just accept the one-time cost of the extra wire and hardware required to string the extra wire for the loop and and run it out of the switchboard of the junction point station.

If the loop went open, or the two wires of it got crossed or grounded, it was a simple matter to just cut it off the main wire at the switchboard until repaired...the only loss of service would be on the branch itself.

Whereas, if a repeater was installed at the junction station, then equipment had to be provided and maintained, personnel provided and trained to do this maintenance, on an ongoing basis.

Except in fairly rare instances, this was far more costly in terms of operating simplicity, equipment and personnel requirements than just running the loop up the branch. Most repeater locations were in the larger city or town Western Union offices.

Examples of loops on RR branches:

Pagosa Spgs from Gato

Manitou from Colorado Springs

Telluride from Vance Jct on the RGS

Magdalena NM from Socorro NM on the AT&SF

etc.

I hope this explains it...Questions, please ask.