Light vs Heavy Construction Battalions
Light construction battalions like the 40th differed significantly from heavy construction battalions in their equipment and mission. While Heavy construction battalions used cable-plowing machines and bulldozers, as well as other heavy construction vehicles to construct semi-permanent open-wire lines, Light construction battalions used portable equipment that could be deployed quickly.
Mission critical tasks for communications within Adsec battalions stressed quick deployment for urgently needed solutions, and were followed up by more permanent installations once the area was fully secured.
Equipment of the 40th Signal Construction Battalion
The 40th used equipment and resources as best as possible, but still needed to set up 30 foot poles in the field where required. They were also instrcuted to use local civilian infrastructure wherever possible, as well as recuperating and re-using materials from infrastructure set up by the enemy.
Poles used by light construction battalions were standard creosoted pine or fir timbers, classified by height and strength for use in open-wire communication lines. They were stored on skids with alternating butt ends to prevent bending and transported on pole trailers or flatcars with balanced loads, the base ends facing forward for stability.
In the field, standard line poles carried the main spans, while heavier or shorter "stub" poles reinforced corners, dead-ends, or steep grades. Each pole was faced and notched ("gained") before installation, ensuring alignment and uniform wire height.
Cable Equipment
Most of the 40th's operations involved the installation of Spiral-4 cable (WF-8/G), a four-conductor cable used for long-distance four-wire telephone and carrier circuits. This cable consisted of four stranded copper conductors insulated and spiraled around a polyethylene core with stabilizing tape and steel braid. It could be used as self-supported aerial line and was supplied in quarter-mile sections with waterproof connectors, making it ideal for rapid deployment.
The battalion also used standard field wire WD-1/TT, a two-conductor field wire weighing about 48 pounds per mile with a tensile strength of roughly 200 pounds. This wire consisted of two individually insulated conductors, each made of four tinned-copper and three galvanized steel strands, twisted together and covered with polyethylene insulation and a nylon jacket.
Crossarms, Insulators, and Pins
Raising poles depended on available equipment. The safest and most common method used a pole derrick or gin pole. The butt was set against a timber "butt-board," side guys and a back guy were attached for stability, and a winch or rope tackle pulled the pole upright. Crews guided it with pikes while ensuring side-guy lines held alignment. Once vertical, the pole was lowered into the hole, lined up with cant hooks, and backfilled and tamped. Proper rigging and teamwork were critical — a well-drilled crew could set a pole quickly and safely, even in rough or unstable terrain.
Pins were short hardwood fittings, usually oak or locust, set into the crossarms to support the glass insulators that carried the wires. Each pin had a tapered, threaded top where the insulator was screwed down, keeping the wire secure and insulated from the wood of the pole.
The insulators were thick, greenish glass with a single deep groove for the wire and a rounded "petticoat" skirt beneath to shed rain and keep the line dry. Most were of the standard single-groove type, but double-groove insulators were used at transposition points where wires crossed, reducing signal interference and keeping communication lines clear in all weather.
Individual Soldier Equipment
Each signalman carried essential personal tools for line construction and maintenance. Climbing spurs were crucial equipment that allowed linemen to scale poles quickly for wire installation and repair. Line tester sets enabled soldiers to check circuit continuity and locate faults in communication lines.
Splicing kits contained the tools necessary to join wire sections together, including specialized connectors and hand splicing tools. Each soldier also carried a lineman's knife for stripping wire insulation and cutting cable. Safety straps and lineman's belts provided essential protection when working at height.
Vehicles
The 40th operated line trucks (K-43 and K-44) equipped with booms, augers, and integral pole derricks for setting poles. These specialized vehicles could handle poles up to 35 feet in length, with the derrick limited by its height relative to the pole's balance point. The auger equipment allowed crews to bore holes in various soil conditions, while the derrick system used winch ropes threaded through sheave blocks to lift and position poles precisely.
Three-quarter-ton and one-and-a-half-ton trucks carried larger cable reels, poles, and construction crews. Two-and-a-half-ton cargo trucks hauled heavy equipment including switchboards, generators, and bulk supplies. Pole trailers were used specifically for transporting the longer telephone poles needed for construction work. Reel deployment systems were mounted on trailers or the ground to allow for the smooth deployment of multi-line jobs.
Mission-Critical Differences
The 40th's equipment reflected their mission to maintain pace with rapidly advancing Allied forces. Unlike heavy construction battalions that built permanent communication infrastructure in rear areas, the 40th needed tools that could be deployed quickly under combat conditions. Their lightweight poles, portable reels, and rapid-deployment cable systems were specifically chosen to support mobile warfare rather than permanent installations.
This equipment allowed the 40th to fulfill their crucial role of maintaining communication links for advancing Allied forces throughout their campaigns in France, Belgium, Netherlands, Luxembourg, and Germany from July 1944 through the end of the war.