These Jefferson Electric Company Coils were used in the good ole days of wireless communications.
The coils are made to step up the voltage and current. They are manufactured to operate on either dry cells or a storage battery, and were guaranteed to give the operator their full rated spark length between the needle points. These coils were made to operate from either 6 or 12 volts. Jefferson Electric Company claimed that the high efficiency of these coils would insure economy in the rate of current consumption so that the life of any battery or dry cells would not be wasted.
When the Jefferson Electric Company manufactured these coils they took special care so that the windings and condenser were balanced to virtually eliminate any arcing at the contact points. This helped to stop or reduce to a minimum any freezing and/or sticking of the points which would help to prolong the life of the points.The points in these coils were made from tungsten. The case of these coils are made from polished mahogany. Most of the metal parts in the example here are made from brass.
These coils were originally intended for items such as signs, automobiles, trains, toys, and anywhere a high tension spark was needed. Early one, two and four cylinder engines used these with batteries to provide ignition. These coils have also been used for the ignition of WWII flame throwers, roofing tar heaters, home heating plants, spark plug testers, fence chargers, railroad track cars, and of course radio spark gap transmitters. Other names for this item is buzz-coil and trembler coil.
The coil has three connecting points. One is for the power source which was usually a battery. The positive from the battery would be connected to this post. The second connecting point was for ground. The third connecting point was the output such as connection to a sparkplug. These coils also have an adjustment called a tension nut. The operator would turn the tension nut until the highest pitched tone was heard from the coil and upon doing so allowed the coil to produce the hottest spark possible.
The Jefferson Electric Company began in January of 1915 in Chicago Illinois and was named after President Thomas Jefferson. The company started with 20 employees and manufactured numerous transformers to be used in signs, automobiles, trains, toys, and so forth. The Jefferson Electric company is still in business to this day and has sales offices in all 50 states.