The small, Syracuse, New York-based company K-II Enterprises makes a number of handheld electronic devices—including the Dog Dazer (a supposedly safe, humane device that deters aggressive dogs with high-pitched radio signals)—but it is best known for the Safe Range EMF. The size of a television remote, the Safe Range EMF detects electromagnetic fields, or EMF, measuring them with a bright LED array that moves from green to red depending on their strength. Designed to locate potentially harmful EMF radiation from nearby power lines or household appliances, the Safe Range has become popular for another use: detecting ghosts.

Since its appearance in the show Ghost Hunters, where the ghost hunter Grant Wilson claimed that it has been “specially calibrated for paranormal investigators,” the Safe Range (usually referred to as a K-II meter) has become ubiquitous among those looking for spirits. Search for it on Amazon, and many listings will refer to it as a “ghost meter,” an indispensable tool in the ghost hunter’s arsenal. It isn’t alone among EMF meters: Of the best-selling EMF meters on Amazon, two out of the top three are explicitly marketed as ghost meters.

Scanning the various product descriptions and reviews, though, what becomes clear is that the K-II Safe Range is a relatively unreliable electromagnetic field meter. It operates only on one axis (you have to wave it around to get a proper reading), and it’s unshielded, meaning that it can be set off by a cell phone, a two-way radio, or virtually any kind of electronic device that occasionally gives off electromagnetic waves. The reviewer Kenny Biddle found he could set it off with, among other things, a computer mouse and a camera battery pack.

Yet it’s precisely because it’s not particularly good at its primary purpose that makes it a popular device for ghost hunters. Erratic, prone to false positives, easily manipulated, its flashy LED display will light up any darkened room of a haunted hotel or castle. Which is to say, its popularity as a ghost hunting tool stems mainly from its fallibility.

The K-II isn’t the only consumer-electronic item used by ghost hunters. Often it’s sold in kits that contain other devices, such as a Couples Ghost Hunt Kit, with two of everything, so you can build “trust and lasting memories when the two of you, alone in some spooky stakeout, look to each other for confirmation of your findings and reassurance!” There are devices that have been engineered specifically for ghost hunters, like a ghost box, which works by randomly scanning through FM and AM frequencies to pick up spirits’ words in the white noise. But mostly, ghost hunters use pre-existing technology: not just EMF meters, but also run-of-the-mill digital recorders, used to capture electronic voice phenomena, or EVP. An investigator records her or himself asking questions in an empty room, with the hope that upon playback ghostly voices will appear.

All of this technology—both the custom and the repurposed—works along more or less the same principle: generating a lot of static and random effects, hoping to capture random noise and other ephemera. The ghost hunter, in turn, looks for patterns, momentary convergences, serendipity, meaningful coincidence. For the believer, this is where ghosts live: in static, in glitches and in blurs.

Ghost hunting was born out of a love of technological failure. In 1861, William H. Mumler, a jeweler’s engraver, was studying the new trade of photography when the shadowy figure of a young girl appeared on a plate he was developing. As Crista Cloutier describes in  The Perfect Medium: Photography and the Occult, Mumler knew it to be an error, a consequence of accidentally reusing a plate that hadn’t been sufficiently scrubbed of its previous exposure. But then he showed the curiosity to a Spiritualist friend of his. “Not at that time being inclined much to the spiritual belief myself, and being of a jovial disposition, always ready for a joke,” he later admitted, “I concluded to have a little fun, as I thought, at his expense.”

He told the Spiritualist that the image was authentic, and that no one else had been around when he’d taken the photograph. His friend took the joke all too seriously, and in short order, Spiritualist publications had reprinted Mumler’s mistake as proof of life after death. Mumler himself soon changed his tune, claiming he’d discovered a “wonderful phenomenon that really needed investigation,” and began offering to make spirit photographs in earnest. For ten dollars (normal sittings cost about a quarter at the time), he’d take your photo, with the proviso he couldn’t guarantee a ghost’s materialization.

Mumler’s inadvertent invention of spirit photography cemented a connection between ghosts and technology that endures to this day—and specifically, the ways that mistakes and accidents of technology appear as manifestations of the paranormal. Consumer technologies from photography to telegraphy to radio to the internet are almost always immediately seized on by believers as offering further proof of the paranormal. In 1953, three children were watching Ding Dong School one afternoon on Long Island when the ghostly face of an unknown woman appeared on the screen. The face would not dissipate, even after the television was turned off, and their father was forced to face the television to the wall “for gross misbehavior in frightening little children,” as The New York Times reported. The television died completely a day later, but not before its paranormal nature had made it a minor celebrity.

For Friedrich Jürgenson, it was a cassette recorder. In the late 1950s, Jürgenson, a painter and filmmaker, was experimenting with recording birds in his garden; when he played them back, he heard voices on the tape that he claimed belonged to his dead father and wife, calling his name. After several years refining his technique, he published his findings in a 1967 book called Radio Contact with the Dead. A few years later, a Latvian psychologist named Konstantin Raudive further developed and elaborated on Jürgenson’s techniques, releasing his own book on the science of recording the voices of the dead in 1971.

Raudive’s transcriptions included some disturbing messages from the beyond. One voice told him: “Here is night brothers, here the birds burn.” Another reported: “Secret reports ... it is bad here.” But Raudive confessed that the ghosts didn’t always speak so clearly. He claimed that spirits would speak in multiple languages, sometimes in the same sentence. Sometimes they would speak backward. Deciphering EVP became a matter of sifting through any acoustic anomaly that shows up on a tape, however minor or incoherent, and then torturing that noise into some kind of meaning.

Electronic voice phenomena have continued to rank among the most prominent “evidence” offered of paranormal activity, it seems, precisely because humans are hardwired to dredge meaning out of chaos. Evolutionarily, we have long needed to discern the sight or sound of a predator despite its camouflage, which has led us to look for patterns where they might not be immediately evident. The quirks and shortcomings of technology plays directly into this biological need: throwing out random static and noise that is primed to be transmuted into meaningful signals. Ghost hunters work through confirmation bias. Looking for proof of the paranormal, they will find it in anything, but most readily in static, gibberish, and errata—technological noise in which we’re hardwired to find false positives.

The only thing that’s changed recently is the proliferation of consumer electronics associated with ghost hunting. In an age of iPhones and Fitbits, ghost hunters are just one more niche market, lapping up the latest and greatest gadgets for sale. But there’s one crucial difference: most purveyors of consumer electronics keep their consumers happy by constantly refining them until they’re free of bugs. Ghost tech works the other way, by actively engineering glitches—the more, the better.

Such seekers can easily be written off as kooks and outliers, but there’s something paradigmatic in their use of faulty devices. The rise of the internet and other new technologies promised a new Information Age, one in which data, truth, and knowledge were the new currency, where the future would be built on information itself. Twenty years on, there’s an endless labyrinth of conspiracy theories, fake memes, trumped up stats, and fabricated evidence. The world’s knowledge is just a Google search away, but it comes to us inextricably intertwined with the world’s bullshit.

The 21st-century media consumer is always working to sift through the noise in search of a signal. Whether it’s a cousin’s anti-vax Facebook post, the endless Farmville requests that have to be filtered out of a feed, or the colossal avalanche of half-truths and lies dumped during this election, most people’s primary challenge online these days is blocking out the endless assault of static, trying to torture it into some kind of meaning.