Being a world-famous inventor means that when national emergencies come up, you get called in to help. That’s what happened in July 1881, when newly elected president James A. Garfield was shot in the back by Charles Guiteau. According to History, the injury should have been non-fatal, but the doctors who worked to assist Garfield couldn’t locate the bullet and made things worse by probing the wound with non-sterile fingers and instruments.

When Alexander Graham Bell heard that doctors could not locate the bullet, he remembered an accidental discovery during his work on the telephone: a method of detecting metal using electricity (via HistoryNet). He immediately began working on what would be the world’s first metal detector, and went to the White House twice to test it. Unfortunately, those tests failed — the results were probably muddied by the presence of metal wires in the president’s mattress. Garfield soon died after weeks of excruciating suffering, mainly because of the infection introduced by his doctors.

However, Bell’s failure with Garfield didn’t deter him. He perfected his metal detector and demonstrated it for doctors (via Britannica). It was eventually adopted by surgeons around the world, and is credited with saving many lives during the early 20th century, most notably during the Boer War and World War I.

Because his family was involved in elocution and speech, and because he had family members who were deaf, Alexander Graham Bell spent much of his energy thinking about sound. In 1877, Thomas Edison invented the phonograph, but as Britannica explains, it was a delicate and unreliable piece of equipment. Edison seemed to lose interest in improving it, and Bell thought he could do better.

It took Bell five years, but he eventually came up with the graphophone. “The Beginner’s Guide to Vinyl” reports the graphophone was a huge leap forward. It used wax instead of tinfoil, resulting in huge improvements in sound quality capabilities. The differences were enough to gain Bell a separate patent from Edison’s invention. The graphophone led directly to the vinyl records that soon brought mass-produced recorded music to the world. Bell co-founded the Volta Graphophone Company in 1886, then sold it along with the patents to the American Graphophone Company, which eventually evolved into Columbia Records.

Incredibly, as noted by Interesting Engineering, Bell’s work on the graphophone almost incidentally resulted in the development of the first working microphones. Prior to that, people had to shout very loudly to use any sort of electronic sound equipment.

Alexander Graham Bell wasn’t the first person to get an aircraft off the ground, of course. The Wright Brothers managed that trick in 1903. But Bell contributed to the early development of flight in a huge way that’s often overlooked today.

The Canadian Encyclopedia notes that Bell’s interest in flight began when he was a young boy, but as reported by Britannica, Bell didn’t begin serious began research into heavier-than-air flight until the 1890s — still long before the Wright Brothers’ historic flight at Kitty Hawk, North Carolina. According to the National Air Force Museum of Canada, Bell formed The Aerial Experiment Association (AEA) in 1907 with the specific goal of building a “practical” aircraft capable of carrying a pilot.

Under Bell’s guidance, the AEA created several gliders, and then turned its attention towards the design of an aircraft. Its solution was the Silver Dart, which took to the air on February 23, 1909 in Nova Scotia — the first powered flight in Canada. It got about 30 feet in the air at a maximum speed of about 65 mph. The Silver Dart was then taken apart and shipped back to Bell’s home in Nova Scotia. Bell’s work in aerodynamics pushed aircraft design forward, improving control and helping to pave the way to modern air travel.

Inventing things is a messy process, even after you unveil your working prototypes. The telephone changed the world, but there’s a difference between something that works a charm in a controlled setting and something that works out in the field where you can’t control variables. Alexander Graham Bell found this out when the telephone started to make its way through the world.

Electronics Weekly reports that people began to notice that when telephone lines ran near electrical lines, the quality of their phone calls dropped significantly due to signal interference. Both telephones and electricity were becoming a growing presence in the world, so the problem was only going to get worse over time. Bell had to come up with a solution.

What Bell came up with was “twisted pair” cabling. PCMag explains that this is when thin wires that are twisted around each other to minimize interference from other wires. Bell received a patent for the invention in 1881. “Dot-Dash to Dot.Com” reports that twisted-pair cabling, augmented with insulating coatings, worked so well that it became standard in all telephone lines and is still used today to provide both land-line telephone service as well as some kinds of broadband internet access.

As explained by Scientific American, people started thinking about using kites to fly themselves around hundreds of years ago. In the late 19th century, Bell turned his attention to creating an aircraft capable of carrying a passenger through the air under power, but a crucial step in his work led to the invention of the tetrahedral kite.

The National Library of Scotland explains that Bell wanted a structure that was light but strong, and scalable enough to carry a man and the engine. He hit on using four-sided polygons called terahedrons — pyramids made up of four triangles — the strongest geometric shape known. The unique properties of the shape allowed the kites to be scaled up dramatically. Bell began designing larger and larger kites using the shape, eventually creating kites large enough to carry humans aloft.

In 1907, Bell created his largest-ever kite, called the Cygnet II. It was towed by a boat over Bras d’Or Lake in Canada, and a man named Thomas E. Selfridge rode on it as it flew. This was a huge step forward in the development of manned aircraft. Unfortunately, as explained in “To Conquer the Air,” making these kites into aircraft powered by engines was incredibly difficult, and Bell’s team slowly lost enthusiasm for the project despite their history-making success.