Pole Line Design, Erection & Inspection

Pole Line Design, Erection & Inspection

SFRR Open Wire March 2015 Topeka 001

South of Topeka, Kansas, Santa Fe lead, 2016.


Double dead-end UPRR long span H-Fixture in Iowa. Note the heavy 5-kV insulated shackles, insulated double head guying and X-brace.

Proper separation and clearance between low voltage alternating current (top 2.4-kV arm) and lower signal, data, telegraph and communications circuits.

REA joint use clearances for open wire and power distribution lines

Many issues with aerial wire come into play at this example: clearance above highway for open wire communications, clearance under 13.2-kV alternating current lines to the left and railway car clearance from easement/bar ditch.

How to tell if a pole used to carry open wire.

Above is a good example of spying a former open wire toll lead route.  Note the “gains” cut into the structure above the cable attachment and 5/8″ bolt hole-on-center locations.  At closer inspection, smaller holes are present where the 30″ span braces were attached with lag screws.  This particular pole line is in north Topeka and operated by Southwestern Bell (now AT&T).  It had over 60 wires (30 pairs) with carrier, D.C. telegraph and voice frequency circuits.  Some may have (in the past) been phantomed, as well.  These bare poles march down a street with only a plastic-sheathed Alpeth cable attached.  Cable size is unknown, but likely is a 200-pair for that location.  The cable pair terminals are all “ready access” units.  Note the risers on the poles where the drops are buried to the homes.  No aerial drops on these poles.

Gaining and drilling designs for open wire and cable facilities


How to Distinguish Each Pair From Another on an OW Line


United Telephone open wire in central Kansas. Photo taken in 1998.


Pin Numbering Systems on Aerial Leads

I’ve often been asked: how can you tell the difference between the pairs if the wires are not colored (as in multi-pair cable) and simply consist of congested-appearing piles of crossarms and wire?


Easy.  Here’s the system used by most telephone companies (and railroads, too):


Take a pole head (the upper portion with the crossarms, braces, pins and insulators). Crossarm pin positions are numbered from left to right, facing along the line in the direction of increasing pole numbers, or where the line is not numbered, in the direction from the C. O. to the field.  Here is an illustration of the methodology for numbering both crossarmed poles and wooden/steel bracket leads.  Sometimes, for other reasons, an unconventional system is used for special circuits, but that is rare.


Crossarms with 16 Pin Positions

First Arm:1-2, 3-4, 5-6, 7-8, 9-10, 11-12, 13-14, 15-16

Second Arm:21-22, 23-24, 25-26, 27-28, 29-30, 31-32, 33-34, 35-36

Third Arm:41-42, 43-44, 45-46, 47-48, 49-50, 51-52, 53-54, 55-56

Crossarms with 10 Pin Positions

First Arm: 1-2, 3-4, 5-6, 6-7, 7-8, 9-10

Second Arm: 11-12, 13-14, 15-16, 17-18, 19-20

Third Arm: 21-22, 23-24, 25-26, 27-28, 29-30

Crossarms with 8 Pin Positions

First Arm: 1-2, 3-4,     7-8, 9-10

Second Arm: 11-12, 13-14,     17-18, 19-20

Third Arm: 21-22, 23-24,     27-28, 29-30

Crossarms with 6 Pin Positions

6A/6B Arm: 3-4, 5-6, 7-8

Crossarms with 4 Pin Positions

4A Arm: 1-2, 3-4

Crossarms or Sidearms with 2 Pin Positions

2A Crossarm: 5-6

How Are Wooden Side Bracket Construction Differentiated for Positions?

Good question, as side brackets may meander all over the sides of a pole due to the non-phantomed or phantomed construction application.  The telephone companies made a subtle difference in their construction by defining their purpose:  For an Exchange bracket lead, the “First Pair” would be: 1-2, the “Second Pair” would be 3-4.  If these were attached to a toll lead, and used for both long distance use and phantomed, the “First Pair” would be 5-6 and the “Second Pair” would be 15-16. That is how it is done.

Facing crossarms at corners on open wire facilities

Facing corners with open wire crossarm design

Bridle wire runs on flat deadends and vertical deadends

Flat dead-ending with a carry through circuit

Single circuit dead-ending with multiple circuit carry through

Actual image example of specification above.

Flat dead-end with carry through facilities