A Closer Look: Mechanical Telephones

In continuing with our newest blog series, I would like to put the spotlight on a recently discovered artifact here at the museum. This new find was uncovered by Dave Silcox, a museum docent and dedicated member of our Friends of Kregel Membership Group. During the Grand Opening and conversations with Kregel family members, there had been mention of a telephone system that had been used to link the two factory buildings very early on in the company's history, however no such telephones had yet been found. The artifacts that were found appear to be the missing telephone system used at the factory.

The type of telephone system used between the buildings is far different from what most would describe as a telephone today, and actually resembles a child's "tin can" string telephone, though a little more sophisticated than Campbell's soup and twine. This type of telephone is referred to as an "acoustic" telephone or a "mechanical" telephone in that it utilizes sound waves through a wire or string instead of a modulated electric current. The design usually consisted of two round diaphragms connected by a line, either string or wire of some sort. When a person would speak into the diaphragm on one end the vibrations from the sound waves traveled down the line to the other diaphragm, emitting the message to the recipient. According to an article published in 1986 by John Kolger entitled Mechanical or String Telephones, there were many different materials used to make the diaphragms and connecting lines and each company that produced these telephones would likely have their own recommendation of what worked best. 

Since the earliest modern style telephones were quite poor in sound quality, the mechanical telephone was a viable alternative for many years. They provided a much higher quality of sound and could pick up much quieter noises than the Bell telephones. According to Kolger, "It is also said that clocks could be heard ticking over the line." This style of telephone wasn't without is downfalls however. Since the line that carried the sound vibrations was exposed to the elements, any sort of inclement weather would affect the sound being produced. Rain or snow hitting the line could cause a tapping noise and ice accumulation could snap the thin connecting line. Another drawback to the mechanical telephone was the fact that the diaphragms at either end of the line needed to be in a straight line to get the best sound out of them, although there were companies that did successfully produce insulators which allowed the line to run at right angles and even switchbacks. Despite the number of companies that produced this type of communication system the technology was fairly short lived and obviously Bell's, and Meucci's, telephone design would win out in the end.

The specific type of telephone that was found was patented and produced by a man named Edwin D. Finch from Stanton, MI. His patent was issued on June 24th, 1879 (US No. 216,840) and was called simply "Improved Mechanical Telephone". Finch's improved design featured a spoke pattern of wires in the middle of the diaphragm, which Finch claimed helped to channel the sound waves down the connecting line to the other end. The face-plates of the telephone system, which are the parts that were found, go over a larger cylinder shaped base. Inside this base, according to Finch's patent, is a chain that allows the wire to be tension to be adjusted easily from either end and for the tension to be released when not in use so as not to wear-out the diaphragm. Another interesting addition to Finch's patent description comes when he is discussing how to get the best sound out of his telephones. He states that the system works best "when the diaphragms at opposite ends of the line are of different material, say one of silk and the other on linen, or vary in size, say a difference of one or two inches in diameter." Finch's description of this reduction in feedback is actually scientifically accurate, not something that can really be said of a lot of older theories regarding how something worked. The difference in diaphragm size or the material it's made from will affect the way in which sound resonated through or over the surface, meaning that once the vibrations reach one end they are less likely to be returned as feedback.

The following are some pictures of Edwin Finch's 1879 telephone system which was used here at the Kregel Windmill Company, and likely the Nebraska City Manufacturing Company before it, in order to communicate between the factory buildings.

The diaphragm ends of Edwin Finch's Mechanical Telephone. Note that one is larger than the other to reduce feedback.

The spoke-shaped wires on the diaphragm that direct sound waves to the connecting line.

Stamp showing the patent date of June 24th, 1879 on the larger of the two diaphragms.

Large diaphragm front showing size. Scale board 1" squares.

Small diaphragm front showing size. Scale board 1" squares.

Be sure to keep checking the blog for more posts regarding upcoming events, museum happenings, and blog series such as "A Closer Look". And, as always, may your blades always catch the wind!