Antique 100-Drop Telephone Switchboards
Sterling, American Electric and Western Electric Made Switchboards
May 19, 2009
During the last twenty years of the 19th century, only three companies were engaged in the manufacture of telephone switchboards. Other switchboards were being constructed by individual artisans who produced one-of-a-kind boards.
Western Telephone Construction Company
Western was located in Chicago, Illinois and produced one of the first 100-drop switchboards in America. It was designed to be mounted directly on a wall or on a partition in an exchange. The drops and jacks were built up between hard-rubber partitions which were shaped much like an egg carton, with each item occupying a single cell. Below the line drops was a row of ten clearing-out drops included in series in the tip side of the cord circuit. This row had a thin metal shield of magnetic material which prevented crosstalk between two neighboring drops.
The plugs were arranged in two rows of ten on the horizontal portion of the table, and in front of them was a row of circuit-changing levers. The entire case containing line-drops was hinged, allowing the board to be opened for repairs. The line wires were bundled into cables, one for each row, and encased in cotton-wrapped silk. The various cables leading to the underside of the table were formed into a bigger, tightly laced cable which then fell beneath the table where they were again allowed to separate and hang by weights.
The crank of the hand-generator was located on the right side of the unit. This was a backup measure that was only used in cases when the power generator failed, which was apparently quite often. As many as six of these units were successfully place side-by-side to make larger switchboards.
Sterling Electric Company of Chicago
Sterling also manufactured a 100-drop switchboard around 1900, and it was a bit more user-friendly and sophisticated than Western’s. The drops were mounted vertically instead of horizontally and the plugs were arranged in two rows which were staggered, making it easier for the operator to reach.
The panel was made of sole-leather which withstood wear and tear very well. Also the answering plugs were shorter than the calling plugs, allowing the operator to leave them attached to the circuit and saving a step when answering a call. The Sterling switchboard also contained a closed cabinet on the back, which enclosed the bundled wires and prevented dust from settling on them.
American Electric Company of New Britain, Connecticut
This switchboard featured thumb-nuts which permitted each set of drops and jacks to be removed when necessary, without disturbing the other wiring in the cabinet. When a line-drop fell, the operator inserted one of the plugs in the row farthest from her into the jack. This action automatically restored the shutter when the collar on the plug engaged the cam on the underside of the shutter.
She then pushed the listening key and found out who the subscriber wanted to call. Next she inserted the mate of the plug into the jack of the subscriber receiving the call. If no power generator was being used, she had to turn the crank of the hand generator while doing this. When the two subscribers finished their call, they each rang off and the line-drops were again activated automatically by the withdrawal of the plugs from the jacks.
By the turn of the twentieth century, telephony had reached several milestones in its history. These switchboard units for small exchanges opened new horizons for bigger and better equipment. They are very scarce and are mostly found in museums.
References:
- Miller, Kempster B., American Telephone Practice, McGraw Publishing Co, 1903.
- Elihu Thomson. Encyclopædia Britannica Online. 18 May. 2009.
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