John Logie Baird’s Televisor: An Early Mechanical TV

Scottish inventor
John Logie Baird had a lot of ingenious ideas, not all of which caught on. His phonovision was an early attempt at video recording, with the signals preserved on phonograph records. His noctovision used infrared light to see objects in the dark, which some experts claim was a precursor to radar.

But Baird earned his spot in history with the televisor. On 26 January 1926, select members of the Royal Institution gathered at Baird’s lab in London’s Soho neighborhood to witness the broadcast of a small but clearly defined image of a ventriloquist dummy’s face, sent from the televisor’s electromechanical transmitter to its receiver. He also demonstrated the televisor with a human subject, who observers could see speaking and moving on the screen. For this, Baird is often credited with the first public demonstration of television.

How the Nipkow Disk Led to Baird’s Televisor

To be clear, Baird didn’t invent television. Television is one of those inventions that benefited from many contributors, collaborators, and competitors. Baird’s starting point was an idea for an “electric telescope,” patented in 1885 by German engineer
Paul Nipkow.

Nipkow’s apparatus captured a picture by dividing it into a vertical sequence of lines, using a spinning disk with perforated holes around the edge. The perforations were offset in a spiral so that each hole captured one slice of the image in turn—known today as scan lines. Each line would be encoded as an electrical signal. A receiving apparatus converted the signals into light, to reconstruct the image. Nipkow never commercialized his electric telescope, though, and after 15 years the patent expired.

The inset on the left shows how the televisor split an image (in this case, a person’s face) into vertical lines. Bettmann/Getty Images

The system that Baird demonstrated in 1926 used two Nipkow disks, one in the transmitting apparatus and the other in the receiving apparatus. Each disk had 30 holes. He fitted the disk with glass lenses that focused the reflected light onto a photoelectric cell. As the transmitting disk rotated, the photoelectric cell detected the change in brightness coming through the individual lenses and converted the light into an electrical signal.

This signal was then sent to the receiving system. (Part of the receiving apparatus,
housed at the Science Museum in London, is shown at top.) There the process was reversed, with the electrical signal first being amplified and then modulating a neon gas–discharge lamp. The light passed through a rectangular slot to focus it onto the receiving Nipkow disk, which was turning at the same speed as the transmitter. The image could be seen on a ground glass plate.

Early experiments used a dummy because the many incandescent lights needed to provide sufficient illumination made it too hot and bright for a person. Each hole in the disk captured only a small bit of the overall image, but as long as the disk spun fast enough, the brain could piece together the complete image, a phenomenon known as persistence of vision. (In a 2022 Hands On column, Markus Mierse explains how to build a
modern Nipkow-disk electromechanical TV using a 3D printer, an LED module, and an Arduino Mega microcontroller.)

John Logie Baird and “True Television”

Regular readers of
this column know the challenge of documenting historical “firsts”—the first radio, the first telegraph, the first high-tech prosthetic arm. Baird’s claim to the first public broadcast of television is no different. To complicate matters, the actual first demonstration of his televisor wasn’t on 26 January 1926 in front of those esteemed members of the Royal Institution; rather, it occurred in March 1925 in front of curious shoppers at a Selfridges department store.

As Donald F. McLean recounts in his excellent June 2022 article “Before ‘True Television’: Investigating John Logie Baird’s 1925 Original Television Apparatus,” Baird used a similar device for the Selfridges demo, but it had only 16 holes, organized as two groups of eight, hence its nickname the Double-8. The resolution was about as far from high definition as you could get, showing shadowy silhouettes in motion. Baird didn’t consider this “true television,” as McLean notes in his Proceedings of the IEEE piece.

In 1926, Baird loaned part of the televisor he used in his Selfridges demo to the Science Museum in London.PA Images/Getty Images

Writing in December 1926 in
Experimental Wireless & The Wireless Engineer, Baird defined true television as “the transmission of the image of an object with all gradations of light, shade, and detail, so that it is seen on the receiving screen as it appears to the eye of an actual observer.” Consider the Selfridges demo a beta test and the one for the Royal Institution the official unveiling. (In 2017, the IEEE chose to mark the latter and not the former with a Milestone.)

The 1926 demonstration was a turning point in Baird’s career. In 1927 he established the
Baird Television Development Co., and a year later he made the first transatlantic television transmission, from London to Hartsdale, N.Y. In 1929, the BBC decided to give Baird’s system a try, performing some experimental broadcasts outside of normal hours. After that, mechanical television took off in Great Britain and a few other European countries.

The BBC used various versions of Baird’s mechanical system from 1929 to 1937, starting with the 30-line system and upgrading to a 240-line system. But eventually the BBC switched to the all-electronic system developed by Marconi-EMI. Baird then switched to working on one of the earliest electronic
color television systems, called the Telechrome. (Baird had already demonstrated a successful mechanical color television system in 1928, but it never caught on.) Meanwhile, in the United States, Columbia Broadcasting System (CBS) attempted to develop a mechanical color television system based on Baird’s original idea of a color wheel but finally ceded to an electronic standard in 1953.

Baird also experimented with stereoscopic or three-dimensional television and a 1,000-line display, similar to today’s high-definition television. Unfortunately, he died in 1946 before he could persuade anyone to take up that technology.

In a
1969 interview in TV Times, John’s widow, Margaret Baird, reflected on some of the developments in television that would have made her husband happy. He would enjoy the massive amounts of sports coverage available, she said. (Baird had done the first live broadcast of the Epsom Derby in 1931.) He would be thrilled with current affairs programs. And, my personal favorite, she thought he would love the annual broadcasting of the Eurovision song contest.

Other TV Inventors: Philo Farnsworth, Vladimir Zworykin

But as I said, television is an invention that’s had many contributors. Across the Atlantic,
Philo Farnsworth was experimenting with an all-electrical system that he had first envisioned as a high school student in 1922. By 1926, Farnsworth had secured enough financial backing to work full time on his idea.

One of his main inventions was the image dissector, also known as a dissector tube. This video camera tube creates a temporary electron image that can be converted into an electrical signal. On 7 September 1927, Farnsworth and his team successfully transmitted a single black line, followed by other images of simple shapes. But the system could only handle silhouettes, not three-dimensional objects.

Meanwhile,
Vladimir Zworykin was also experimenting with electronic television. In 1923, he applied for a patent for a video tube called the iconoscope. But it wasn’t until 1931, after he joined RCA, that his team developed a working version, which suspiciously came after Zworykin visited Farnsworth’s lab in California. The iconoscope overcame some of the dissector tube’s deficiencies, especially the storage capacity. It was also more sensitive and easier to manufacture. But one major drawback of both the image dissector and the iconoscope was that, like Baird’s original televisor, they required very bright lights.

Everyone was working to develop a better tube, but Farnsworth claimed that he’d invented both the concept of an electronic image moving through a vacuum tube as well as the idea of a storage-type camera tube. The iconoscope and any future improvements all depended on these progenitor patents. RCA knew this and offered to buy Farnsworth’s patents, but Farnsworth refused to sell. A multiyear patent-interference case ensued, finally finding for Farnsworth in 1935.

While the case was being litigated, Farnsworth made the first public demonstration of an all-electric television system on 25 August 1934 at the Franklin Institute in Philadelphia. And in 1939, RCA finally agreed to pay royalties to Farnsworth to use his patented technologies. But Farnsworth was never able to compete commercially with RCA and its all-electric television system, which went on to dominate the U.S. television market.

Eventually, Harold Law, Paul Weimer, and Russell Law developed a better tube at their Princeton labs, the image orthicon. Designed for TV-guided missiles for the U.S. military, it was 100 to 1,000 times as sensitive as the iconoscope. After World War II, RCA quickly adopted the tube for its TV cameras. The image orthicon became the industry standard by 1947, remaining so until 1968 and the move to color TV.

The Path to Television Was Not Obvious

My Greek teacher hated the word “television.” He considered it an abomination that combined the Greek prefix
telos (far off) with a Latin base, videre (to see). But early television was a bit of an abomination—no one really knew what it was going to be. As Chris Horrocks lays out in his delightfully titled book, The Joy of Sets(2017), television was developed in relation to the media that came before—telegraph, telephone, radio, and film.

Was television going to be like a telegraph, with communication between two points and an image slowly reassembled? Was it going to be like a telephone, with direct and immediate dialog between both ends? Was it going to be like film, with prerecorded images played back to a wide audience? Or would it be more like radio, which at the time was largely live broadcasts? At the beginning, people didn’t even know they wanted a television; manufacturers had to
convince them.

And technically, there were many competing visions—Baird’s, Farnsworth’s, Zworykin’s, and others. It’s no wonder that television took many years, with lots of false starts and dead ends, before it finally took hold.

Part of a continuing series looking at historical artifacts that embrace the boundless potential of technology.

An abridged version of this article appears in the September 2024 print issue as “The Mechanical TV.”