With the AT&T Long Lines microwave relay network being built for reliability — including being able to remain operable during a nuclear attack — having an uninterruptible power supply was crucial.
Accidents, natural disasters and the aforementioned apocalyptic attack could all knock out electrical power to a relay site for days, weeks or even months. Thus, having a reliable way to power the site on its own was imperative. All Long Lines microwave relay sites — from the small, unmanned terminal repeater on a spur route with only one hop, to large bunkers with several stories underground — had backup power generator sets to keep the site online when the utility power went out.
Unmanned repeater sites
The style of generators used by Long Lines varies depending on region, date the site was constructed, and whether it is the original generator or a replacement. Nearly all unmanned repeater sites utilized some form of diesel backup generator.
Today, many of the original generators have either been retired in place and/or replaced by newer, more efficient generators that run on natural gas or liquefied petroleum/propane.
General Motors/Detroit Diesel KS-1958x
Perhaps the most common of all generators used by Long Lines was the Western Electric KS-1958x series, which was manufactured for Western Electric (the manufacturing arm of the Bell System) by the Detroit Diesel division of General Motors. They were the true workhorse, powering most unmanned repeater sites built anytime in the 1950s and 1960s.
Most of these generators were built around a 12-cylinder GM/Detroit diesel engine that typically pulled air directly from outside the base station building through an intake vent, which crossed over the engine’s cooling radiator. Opposite the air intake and radiator was the large alternator used to turn the engine’s mechanical power output to electrical power.
Brian Adams shared these videos of the original General Motors/Detroit/Western Electric KS-19585 diesel backup generator at the Sublette, Kansas, site running. The station is used as a transmitter site for a low-power television station.
Other generators
Other types of generators — including Kohler, Hercules and other brands — have been found in unmanned Long Lines repeater sites.
International-Harvester Solar turbine generators
Large bunkers and central offices used as microwave and cable repeaters, among other responsibilities, had far greater power needs than the unmanned repeater sites.
The Bell System deployed Solar Saturn turbine generator sets in many of its larger sites throughout the 1960s. Manufactured by the Solar division of International-Harvester, these large generator sets were built around a 1,100-horsepower Saturn turbine engine to rev the alternator at 1,200 rpm — producing 750 kilowatts of electricity. According to a brochure posted on Albert LaFrance’s website, International-Harvester also produced a smaller 200 kilowatt model for use by in the Bell System’s smaller sites. The engines ran on kerosene, JP-4 or No. 2 diesel fuel. The brochure said the 750-kilowatt model burned 95 gallons of fuel per hour, with the smallest 188-kilowatt model burning 51 gallons of fuel per hour.
Dimensions printed in the brochure showed the 750-kilowatt model as being 50 inches wide, 202 inches long and 76¼ inches tall. Many of the Solar turbines were installed in underground bunkers, usually in pairs for even more redundancy. The exhaust area was typically fenced off with a sign warning of exhaust temperatures exceeding 500 degrees Fahrenheit. (According to the brochure, the maximum exhaust temperature could exceed 900 degrees Fahrenheit.)
The brochure also detailed the “Solar Gas Turbine School”, which covered various aspects of the generator sets — from the turbine engine to the alternator to controls. “Not only the turbine engine is covered but also the entire package.”
White-Superior diesel generators
Older bunkers and large facilities, typically in the eastern United States, featured large Superior and White-Superior diesel gensets of a more conventional design.
General Motors Electro-Motive Diesel generators
Anyone familiar with trains and locomotives may know where this is heading.
Several large installations — including AT&T’s massive Norway, Illinois complex that served as a major switching hub as well as microwave relay site — used General Motor’s Electro-Motive Diesel generators. These generators are often found powering locomotives, which often actually use electrical motors — powered by the diesel generator — for propulsion.
A member of the Facebook Group said two GM-EMD generators were installed at Norway, with a pad for a third generator that was never installed.
Allis-Chalmers generators
According to a AT&T Long Lines Facebook Group user, the Bell System mainly installed Allis-Chalmers generator sets in facilities of greater concern to the United States government. An example photo they posted depicted a 12-cylinder Allis-Chalmers engine installed in such a facility that has since been abandoned.
Grid interface and other equipment
All generators were designed to start automatically upon a utility power outage. Panels were typically installed, either near the genset itself or the facility’s electrical distribution switchgear, to monitor the utility power and start the genset upon power failure.
On “semi-hardened” and some underground facilities, the generator air intake vents were covered with a “blast shield” to protect it from a nuclear blast. For instance, all concrete “semi-hardened” facility along the Kansas City-Halifax-Oakdale, Illinois, route had a blast shield protecting the intake. Above the blast shield is the generator exhaust.
Generators were tested frequently to ensure they would function during a power outage. For proper testing, a dummy load was necessary to pull current from the generator. Many sites with the “blast shields” used heaters installed at the top of the two exposed sides of the shield, mounted between the shield wall and building.
