History Of Cordless Telephone Invented By Alexander Graham Bell

You might have learned science in school where Alexander Graham Bell was the first known man to create the world's first telephone. However, some might disagree with this as they believed the credit should go to Antonio Meucci for being the first telephone innovator in the world.

Despite this story being linked to him being the first creator of the telephone, it is in fact not the case as Alexander Graham Bell's greatest creation will be the photophone instead.

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On 3 June 1880, Alexander Graham Bell sent a message from the first cordless telephone, which he called the photophone. It is a device that allowed the sending of sound on the beam of light. This event occurred 19 years before the first transmission of wireless radio.

Bell described his photophone as the biggest achievement in his life, but unfortunately, Bell's work was not recognized fully at the time. It will be another century before Bell's hard words will be highly appreciated.

What is a Photophone?

A photophone is a device somewhat similar to a contemporary telephone except it utilizes modulation light as a means of wireless transmission and not electrical modulation that is carried through wires.

In simpler terms, a photophone comprises a flexible plane mirror where the back is where the loudspeaker for the sound is directed. The air pressure generated by the voice will cause the flexible mirror to vibrate turning it into a convex and concave mirror alternately. This will ultimately deliver and adjust the light alternately as well.

The stronger beam of light will be reflected from this vibrating mirror. If we observe it closer to the location of the receiver, the beam of light can be seen throbbing in correlation with the frequency of the sound wave that reacts to the mirror.

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But converting the throbbing light into sound has proven very difficult for Bell. In one experiment, Bell created a receiver from black carbon dust(known as Carbon black or Lamp black). It produces a tone that is described as very painful to the ears when pressed close to the device.

The Greatest Creation

The photophone was created together by Alexander Graham Bell and his assistant, Charles Summer Tainter on 19 February 1880 in the Bell lab at 1325 L Street, Washington, D.C. Both of them later became full members of the Volata Laboratory and Bureau which was created and sponsored by Bell.

On 3 June 1880, Bell's assistant managed to send a wireless voice message from the roof of Franklin school to the window of Bell's lab which was around 213 meters apart.

Bell believed that the photophone he created is his most crucial invention. Of the 18 patents registered under Bell's name and 12 being shared with his partners, 4 of them are for his photophone which Bell refers to as his greatest creation.

He once told reporters before he passed away that the photophone he created will be far much superior that the telephone that has been invented.

The photophone is the pioneer in the optic replacement communication system that reached its popularity in the whole world starting in the 1980s. The parent patent for the photophone(U.S. Patent 235, 199 Apparatus for Signalling and Communicating, known as Photophone) was issued in December 1880, several decades before the principles starts to be practically applied.

Challenges and Obstacles

The question will be if Bell himself felt that the photophone he created is his best creation yet, why most people to this day still do not know about his invention?

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At that time, Bell hoped the new photophone will be used by ships in the ocean. He also envisioned that wireless communication will replace the telephone lines that are scattered along the streets of cities across the globe.

The photophone was accepted to be used by the German Navy in the early 20th century. The German physicist, Ernst Ruhmer created a signal receiver that is used to send signals from as far as 15km by using high-powered light provided by the Navy.

Siemens & Halske company issued the units commercially for the German Navy that offers communication up to 11 km in distance by using a voice-modulated searchlight. The British and American have taken the initiative to make some improvements to the Bell system during the First World War.

Unfortunately, Bell failed to protect the transmission from outside interference such as clouds, mist, rain, snow, and other things that can interfere with the transmission of light easily.

Not long after, the Marconi radio transmission started to surpass the maximum range of the photophone. To this day, the beam of light is the main information carrier around the world despite it not being in the form expected by Bell.

The transmission of light signals wirelessly, it can now be replaced by optic cables across the continents.

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