In this blog post, we’ll provide an intuitive explanation of the history and operating principles of mechanical televisions.

Introduction: The Emergence of TV and Contemporary Reactions

George Orwell’s novel “1984,” published in 1949, depicted a bleak future where people were constantly monitored by screens everywhere. While some may recall the novel’s ominous vision when they see modern society surrounded by various screens, it is interesting to note that such concerns already existed in the early days of television.
One of the most commonly told anecdotes about the early days of television comes from the son of John Logie Baird. When the first television broadcasts began via the BBC in the UK, people had two main concerns. One was a practical worry that the flickering light from the screen might damage their eyes, and the other was a fear that someone might be watching them from beyond the screen. Thus, it can be said that vigilance against “Big Brother” began with the advent of television.
As evidenced by people’s somewhat exaggerated reactions at the time, the invention of television was a revolution. Often regarded as one of the defining inventions of the 20th century, television evolved from the thick, bulky cathode-ray tube (CRT) sets of just a few decades ago through LCD, PDP, and LED technologies into thin, high-definition large screens, and has recently even become capable of displaying 3D images.

The Birth of Mechanical Television and the Nipco Disc

However, as with all technology, the first television was not perfect. While many people remember the first TV as an electronic CRT, the very first TV actually operated mechanically, not electronically. The word “television” is a compound of “tele” (meaning “far”) and “vision” (meaning “to see”), representing a fusion of communication and display technologies. Strictly speaking, early mechanical TVs are sometimes called “electromechanical televisions” because they used electronic systems for communication and mechanical systems for display.
The Nipkow disk, invented in 1884 by German inventor Paul Nipkow, is considered the precursor to television technology. This device works by drilling holes in a spiral pattern on a metal disk and rotating it. The principle is that when light entering through the holes on the disk is modulated according to an electrical signal, the light passing through the holes is projected onto a screen on the opposite side.
This may raise the question, “How does the light passing through the holes create a moving image?” and this is precisely the key point. The principle behind the Nipkow disk is similar to that of early cinema. Movies project a rapid sequence of still images, which our eyes perceive as motion. Mechanical TVs utilized a similar principle of continuity, but differed in that they had to “transmit image information over long distances using only electrical signals.”
At the time, communication technology did not have sufficient bandwidth to transmit the entire image of a single frame as an electrical signal. Since it was not possible to transmit data at gigabyte-per-second rates via digital communication as we do today, transmitting entire frames was not a practical solution. The Nipco disk solved this problem.
The Nipco disk features multiple concentric tracks on a disc, with each track divided at specific angles and perforated with holes. This structure is easy to understand if compared to a mass game. Each track corresponds to a single line on the screen, and as the holes in each track rotate, light is projected onto the screen line by line, moving sequentially from the top to the bottom of the screen. By adjusting the brightness of the light according to electrical signals, the contrast of each line is rendered.
Strictly speaking, only a single dot is visible on the screen at any given moment, but the human eye has a tendency to perceive a series of dots as a single line. This is the same principle as when a container filled with embers is spun rapidly during a traditional Korean firework display, causing it to appear as a circle to our eyes. If the disk is spun fast enough, each line is displayed sequentially, ultimately appearing as a single image.

Resolution, Information Volume, and Examples of Operation

The resolution of a mechanical TV is determined by the number of tracks (or lines). The mechanical TV demonstrated by John Logie Baird had about 30 tracks, which effectively divided the screen into 30 thin lines, resulting in a resolution just high enough to barely make out a human face.
The advantage of this method is that it drastically reduces the amount of information required. Since knowing only the brightness of a single point passing through a hole is sufficient to represent a single line of the screen, transmission was possible using only a brightness signal (voltage waveform) that changes over time. A simple voltage signal carries just enough information to be transmitted over a single wire without separate compression, enabling the long-distance transmission capability implied by the prefix “tele.”
It is easier to understand with an example. Assuming the disc has 30 tracks and rotates 600 times per minute, the disc completes one rotation in 0.1 seconds. This 0.1-second interval is evenly distributed among the 30 tracks, so each track displays one line for approximately 0.0033 seconds. For example, from 0 seconds to 0.0033 seconds, the lighting brightens and dims according to the voltage to depict a person’s eyebrow, and from 0.0033 seconds to 0.0066 seconds, it moves to the next line to depict the eye.
Of course, the entire face never appears on the screen at any single moment. However, in 0.1 seconds, all tracks sequentially complete the screen, and since this process repeats 10 times in 1 second, the human eye perceives it as a single continuous image and recognizes it as moving video.

Limitations and Historical Significance

Although it was the first TV with such an intuitive operating principle, mechanical television could not overcome its fatal flaws: poor resolution and constant flickering. Compared to today’s technology, which divides the screen into millions of pixels to produce natural-looking images, the resolution of just a few dozen lines at the time was severely limited. Furthermore, due to the nature of the device, the light had to flash continuously, making the screen appear unnatural.
Ultimately, the mechanical TV that debuted in 1926 did not last long and was replaced by the electronic CRT system around 1930. Today, mechanical TVs can only be found in museums or historical records, but their invention clearly heralded the birth of a new medium and had a profound impact on modern society as a whole. Following Baird, the efforts of countless inventors, scholars, and entrepreneurs continued, leading television technology to gradually become more complex and reach the level of sophistication we see today.