In today’s world can you imagine a life without television? Have you ever wondered who invented mechanical television?
Mechanical Television was invented by John Logie Baird in 1925. John Baird was among was few inventors who were experimenting on sending moving images by using radio waves.
John was a Scottish inventor who gave demonstration to group of Scientist in London. John named his invention “televisor” and he was successful in demonstrating the image of person working a ventriloquist doll. Group of 50 scientists were shown large wooden disc which had lenses in it.
Behind this disc revolving shutter and light sensitive cells were kept. John explained that with help of shutter and lens of disc images of people or objects placed in front of machine could be passed at high speed over the light sensitive cell.
Based on the proportion of the light falling on the cell the current varies and this current in varied proportion gets transmitted to the receiver. The final image that was shown as transmitted was not very clear and was blurred however this experiment proved that moving images can be transmitted from one place to other.
Baird’s Televisor ( Credits: Vox)
John Baird’s television was shown in 1927 where pictures were transmitted between London and Glasgow thereby covering the distance of around 438 miles. Immediately next year Baird was able to transmit pictures between to London and Newyork thus once again received credit for first transatlantic television transmission.
In 1930 the BBC made available the second transmitter to Baird and he was then able to make a program that simultaneously transmits both sound and picture. Earlier due to limited bandwidth either sound or picture could be transmitted both these components could not be transmitted together.
Further, John Baird also invented colour television. Thus in the history of television John Baird held a prominent place. His contribution was also celebrated by Google with special Google doodle to mark the 90th anniversary of his first demonstration of televisor.
How Does a Mechanical Television Work
Then the mechanical TV further underwent many changes. In order to understand how today’s mechanical television works one needs to be divide TV into two main parts. First part includes the circuitry which generates image data and the second part is the mechanical action which converts image data into picture.
Mechanical TV uses Nipkow disc which is a disk that has holes in it and each hole is slightly lower than the other hole. These discs are rotating disks present at both the transmitter and the receiver end.
The camera is then placed in a room that is completely dark. Nipkow disc is exposed to a bright light from behind. A motor is used to rotate this disk therefore Nipkow disc for every frame of the television picture makes one rotation. The disc made by Baird had thirty holes and it rotated 12.5 times in one second.
A lens is placed in front of the disk which focuses on the object that needs to be telecasted. As soon as the light hits the object it gets reflected into photoelectric cell. Photoelectric cell then converts the energy of light into electrical impulses.
The dark areas of the subject either do not reflect or reflect very little light and thus very little electrical impulse is produced however the bright area of the object reflects more light and produces higher degree of electrical impulse.
Thus once can now also make simple mechanical television at home as well however there is no argument on the fact the inventions of mechanical television is one of the revolutionary event that has changed the definition of media.
These electrical impulses then get amplified and then transmitted to the receiver and as mentioned earlier receiver end also has Nipkow disc which is being rotated by the help of motor as the same speed as that of the disk present at transmitter end (near the camera). The two motors are synchronized using many types of methods.
In practice a neon lamp is placed behind the disk. The videos transmissions are picked up by a radio receiver which is then connected to the neon lamp.
Now the disc rotates and the neon lamp emits light in proportion to the electrical impulses sent by the receiver. If the area of subject is dark very little light output is received and for bright areas more light output is received. Thus image gets transferred to the other disk with the help of magnifying glass.