Bell's First Transmitter
Alexander G. Bell's first transmitter was demonstrated on March 10, 1876. It was then that Bell spoke the famous words, "Mr. Watson, come here, I want to see you." The first version was based on the changing resistance caused by a vibrating needle inserted into a small bath of conductive acid. See Fig A1 from Bell's notebook.
This model was not practical for many reasons one being the strict need to keep the needle a hair's breadth below a level surface of the liquid. Apparently, he tried many liquids including water (no sound), cod liver oil (no sound), salt water (sound). A mixture of water and sulphuric acid seemed to work best.
Fig A1, A.G. Bell's first demonstrated telephone transmitter
The needle, W, vibrated in step with its attached diaphragm as speech was uttered into mouthpiece M. As the needle vibrated, the resistance varied slightly between W and P, a fixed electrode immersed in the bath. A battery supplied current and this was modulated by the varying resistance. The changing current actuated a receiving coil attached to a flexible surface that emitted the corresponding sound waves. Bell tested this version and was beyond happy when Watson heard him speaking.
From a letter (Library of Congress) to Alexander G. Bell's father on the same day, Bell wrote,
"Dear Papa, .....This is a great day with me. I feel that I have at last struck the solution of a great problem — and the day is coming when telegraph (Bell's description for telephone lines) wires will be laid on to houses just like water or gas and friends converse with each other without leaving home."
How true are his words! In time, Bell developed other transmitter models that proved more practical. Plus, Bell worked with other inventors, such as Blake (see below) and Edison, to improve on his work.
Interestingly, Bell was granted patent US174,465A on March 7, 1876, three days before his famous speaking demo with Watson on March 10. Reviewing the patent, Bell describes a completely different type of transmitter using electro-magnets. Likely a method, as described, he never made work. Nonetheless, the five Claims of the patent (the most important section of any patent) cover the general case of transmitter, wire, battery, and receiver such that the patent stood the test of time against many lawsuits.
For example, Claim #4, "The method of producing undulations in a continuous voltaic circuit by gradually increasing and diminishing the resistance of the circuit, or by gradually increasing and diminishing the power of the battery, as set forth." This claim is very broad and covers many transmitter methods including the one in Fig A1.
This author had a plan to build a replica of Bell's first transmitter then stumbled on an excellent YouTube video by Wayne Campbell. Wayne recreates Bell's transmitter and documents his steps ending with a working demo. Wayne's model is based on Bell's notebook writings and the image in Fig A1. Hope you enjoy the explainer video as much as I did.
Francis Blake: An Unsung Hero?
(This article was originally published by the Microwave Journal, November, 2023, author Eric Higham.)
The Time Travel feature highlights the early pioneers that have helped shape the trajectory of the electronics industry. Since we started this feature, we have profiled Max Planck, Nikola Tesla, Guglielmo Marconi, James Clerk Maxwell, Hedy Lamarr and Oliver Heaviside, all recognizable names. As I started thinking about the November profile, I saw that Francis Blake was granted a U.S. patent in November 1881 for the “Speaking Telephone” and thought “who?”
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It turns out that Francis Blake (1850-1913) was born in Newton, Mass., less than 10 miles up the road from the Microwave Journal Offices. He began working as a scientist with the U.S. Coast Survey at 15. In 1874, Blake married into a very wealthy family, allowing him to leave his job and pursue his passions as an inventor and later, a photographer.
This is where the story gets interesting for the electronics community. Alexander Graham Bell received a U.S. patent for the telephone in 1876, but by most accounts, the business he started was struggling. Bell’s telephone received calls, but it did not transmit them very well or very loudly. At the time, Western Union was Bell’s main competitor, and they were using a carbon-based transmitter from Thomas Edison that performed much better.
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When Blake learned of the telephone patent, he began experimenting to improve the quality of the transmitter. For the next two years, he worked with Bell employees to refine the design to correct a whole host of resonance, mounting, contact point and material issues. In 1878, satisfied that he had a viable improvement, Blake took his transmitter to the Bell offices and after thorough testing by Thomas Watson, the person who received Bell’s first phone call, the Bell Company bought Blake’s design.
Early Telephone with Blake Transmitter on the left
London Science Museum
Feeling confident that they had a transmitter that was as good as or better than what Edison had developed for Western Union, the Bell Company sued Western Union for patent infringement and won. Western Union settled out of court and surrendered all its patents and telephone business to the smaller Bell Company. From these beginnings and armed with the patent and the “Blake Transmitter,” as it became known, the Bell Company grew into Bell Telephone, a behemoth that had revenues of more than $400 billion with more than one million employees before it was broken up in the early 1980s.
The proceeds from the sales and licensing of the Blake Transmitter made Francis Blake independently wealthy. In 1884 he took up photography and it quickly became a passion. In 1885, Blake purchased an instantaneous shutter camera, which meant a shutter speed of about 1/300th of a second. Not satisfied, Blake designed a focal plane shutter that allowed shutter speeds of 1/1000th -1/2000th of a second. This allowed stop-action photographs of moving objects that were quite different from what was common at the time.
Francis Blake was a bit of a Renaissance person with his interests and inventions. He rubbed shoulders with the people credited with developing the U.S. phone industry, but he did not have that notoriety. His Blake Transmitter was widely used for 20 years after it was patented, and it was credited with speeding up the development and deployment of telephony in the U.S. So, the answer to my question of “who?” is a man who may be the unsung hero of an industry that is currently approaching $2 trillion in revenues. (END)
There were many inventors working feverishly on improved microphone transmitters in the early years. Bell's first microphone was deficient in many ways so he and Watson were on the hunt for an improved version.
The development history is abundant with claims and counter-claims over who invented the "transmitter" with its many versions. One thing is sure, Blake had an important role and his version became the favorite of the Bell company.
Blake Transmitters dominated telephony from 1878 to about 1890, with many still in use long after. See https://ethw.org/Telephones#Variable_Resistance_Transmitters for more details.
Below is an image (1880-1900) from the London Science Museum. On the right side of the telephone is a Blake carbon button microphone.
