Engraving of Alexander Graham Bell's photophone, showing the receiver and its optics

Replica Of 1880 Wireless Telephone Is All Mirrors, No Smoke

April 15, 2025 by Tyler August 18 Comments

If we asked you to name Alexander Graham Bell’s greatest invention, you would doubtless say “the telephone”; it’s probably the only one of his many, many inventions most people could bring to mind. If you asked Bell himself, though, he would tell you his greatest invention was the photophone, and if the prolific [Nick Bild] doesn’t agree he’s at least intrigued enough to produce a replica of this 1880-vintage wireless telephone. Yes, 1880. As in, only four years after the telephone was patented.

It obviously did not catch on, and is not the sort of thing that comes to mind when we think “wireless telephone”. In contrast to the RF of the 20th century version, as you might guess from the name the photophone used light– sunlight, to be specific. In the original design, the transmitter was totally passive– a tube with a mirror on one end, mounted to vibrate when someone spoke into the open end of the tube. That was it, aside from the necessary optics to focus sunlight onto said mirror. [Nick Bild] skips this and uses a laser as a handily coherent light source, which was obviously not an option in 1880. As [Nick] points out, if it was, Bell certainly would have made use of it.

Bell's selenium-based photophone receiver. — The photophone receiver, 1880 edition. Speaker not pictured.

The receiver is only slightly more complex, in that it does have electronic components– a selenium cell in the original, and in [Nick’s] case a modern photoresistor in series with a 10,000 ohm resistor. There’s also an optical difference, with [Nick] opting for a lens to focus the laser light on his photoresistor instead of the parabolic mirror of the original. In both cases vibration of the mirror at the transmitter disrupts line-of-sight with the receiver, creating an AM signal that is easily converted back into sound with an electromagnetic speaker.

The photophone never caught on, for obvious reasons — traditional copper-wire telephones worked beyond line of sight and on cloudy days–but we’re greatful to [Nick] for dredging up the history and for letting us know about it via the tip line. See his video about this project below.

The name [Nick Bild] might look familiar to regular readers. We’ve highlighted a few of his projects on Hackaday before.

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Retrotechtacular: The 1951 Telephone Selector

January 11, 2025 by Al Williams 20 Comments

Telephone systems predate the use of cheap computers and electronic switches. Yesterday’s phone system used lots of stepping relays in a box known as a “selector.” If you worked for the phone company around 1951, you might have seen the Bell System training film shown below that covers 197 selectors.

The relays are not all the normal ones we think of today. There are slow release relays and vertical shafts that are held by a “dog.” The shaft moves to match the customer’s rotary dial input.

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Building A 3D Printed Phone Handset With Mil-Spec Style

December 28, 2024 by Tom Nardi 14 Comments

In general, military gear is designed to be rugged and reliable. A side effect of this is that the equipment usually has a distinct visual look that many people find appealing. You might not need a laptop that can survive being in a war zone, but plenty of hackers have picked such machines up on the second hand market anyway.

Case in point, the H-250 telephone handset. [Tobias] didn’t actually need a combat-ready phone handset, but loved the way it looked. Technically you can pick these up on eBay for a reasonable price, but then you’ve still got to deal with the weirdo military components inside it. So why not design a look-alike and 3D print it?

[Tobias] came up with a design in OpenSCAD that has a very close resemblance to its military counterpart. Not only has he made the source code for the 3D model available for others who might want to print their own look-alike handset, but the Hackaday.io page also includes a breakdown of the hardware that needs to be added to the printed parts to make it a functional handset.

If you think the H-250 handset looks familiar, it’s probably because it comes standard issue on the TA-1042 field telephone — another very slick looking piece of military gear that we’ve covered previously.

World’s First Virtual Meeting: 5,100 Engineers Phoned In

November 16, 2024 by Heidi Ulrich 11 Comments

Would you believe that the first large-scale virtual meeting happened as early as 1916? More than a century before Zoom meetings became just another weekday burden, the American Institute of Electrical Engineers (AIEE) pulled off an unprecedented feat: connecting 5,100 engineers across eight cities through an elaborate telephone network. Intrigued? The IEEE, the successor of the AIEE, just published an article about it.

This epic event stretched telephone lines over 6,500 km, using 150,000 poles and 5,000 switches, linking major hubs like Atlanta, Boston, Chicago, and San Francisco. John J. Carty banged the gavel at 8:30 p.m., kicking off a meeting in which engineers listened in through seat-mounted receivers—no buffering or “Can you hear me?” moments. Even President Woodrow Wilson joined, sending a congratulatory telegram. The meeting featured “breakout sessions” with local guest speakers, and attendees in muted cities like Denver sent telegrams, old-school Zoom chat style.

The event included musical interludes with phonograph recordings of patriotic tunes—imagine today’s hold music, but gloriously vintage. Despite its success, this wonder of early engineering vanished from regular practice until our modern virtual meetings.

We wonder if Isaac Asimov knew about this when he wrote about 3D teleconferencing in 1953. If you find yourself in many virtual meetings, consider a one-way mirror.

How The Bell System Was Built

July 15, 2024 by Al Williams 9 Comments

We’ve often thought that while going to the moon in the 1960s was audacious, it was just the flashiest of many audacious feats attempted and accomplished in the 20th century. Imagine, for a minute, that the phone system didn’t exist today, and you stood up in front of a corporate board and said, “Let’s run copper wire to every home and business in the world.” They’d probably send you for a psychiatric evaluation. Yet we did just that, and, in the United States, that copper wire was because of the Bell system, which [Brian Potter] describes in a recent post.

The Bell company, regardless of many name changes and divisions, was clearly a very important company. [Brian] points out that in 1917, it was the second-largest company in the United States and continued to grow, eventually employing a whopping 1% of the entire U.S. workforce. That’s what happens when you have a monopoly on a product that is subject to wild demand. In 1900, Bell handled 5 million calls a day. By 1925, that number was over 50 million. In 1975, it was just shy of 500 million. If Wester Electric — just one part of Bell — was its own company, it would have been the 12th largest company in the U.S. during the 1970s.

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SIPing A Vintage Phone

June 16, 2024 by Jenny List 5 Comments

Something that’s a bit of fun at hacker camps such as the recent EMF Camp is to bring along a wired phone and hook it up to the on-camp copper network. It’s a number on the camp network, but pleasingly retro. How about doing the same thing at home? Easy enough if you still have a wired landline, but those are now fast becoming a rarity. Help is at hand though courtesy of [Remy], who’s written about his experiences using a 1960s Dutch phone as a SIP device.

The T65 was the standard Dutch home phone of the 1960s and 1970s, and its curvy grey plastic shape is still not difficult to find in that country. The guide covers using various different VoIP boxes between such an old machine and the Internet, but there’s more of interest to be found in it. In particular the use of an inline pulse-to-tone converter, either the wonderfully-named DialGizmo, or perhaps closer to our world, a PIC-based kit.

So if you can lay your hands on a VoIP box it’s completely possible to use an aged phone here in 2024. Remember though, a SIP account isn’t the only way to do it.

J. de Kat Angelino, CC BY 3.0.

Why Your Old Phone Sounded The Way It Did

June 2, 2024 by Jenny List 26 Comments

The mobile phone may be sweeping away the traditional wired phone, but that doesn’t change the fascinating history and technology of the older device. At [This Museum Is Not Obsolete] they have a fully functional mechanical telephone exchange as one of their exhibits, and they’ve published a video examining the various sounds it’s capable of making.

When a voice synthesiser was the stuff of science fiction, exchange status couldn’t be communicated by anything but a set of different tones. If you’ve ever encountered a mechanical exchange you’ll recognise the harsh-sounding low-frequency dial tone, and the various sets of beeps denoting different call status. These were produced with a set of oscillators being switched in and out by shaped cams, and the bank of these on their exchange is most of the subject of this video. The common ones such as the engaged tone and the dial tone are explained, but also some we’d never heard such as the one signifying the exchange as out of capacity.

We may never own a mechanical exchange of our own, but we’re glad that someone does and is sharing it with us. You can see the video below the break.

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