Poor Tesla. He probably had no idea when he passed electricity through his body to light a bulb that the concept would eventually be used for certain… nefarious purposes. (Or maybe he did, that manly minx.) January 7 marks 75 years since the inventor and engineer’s death, so to honor his legacy, we think it’s time to look at the steamier aspect of alternating current: electrosex. Also known as e-stim (electrostimulation), or stimming. Basically, it’s passing an electric current through your sensitive bits in order to induce pleasure or orgasm. It’s also the purveyor of the elusive HFO—the much desired hands-free orgasm. Fair warning now, there are a lot of wires and metal bits involved. But don’t be scared. It’s actually a lot easier than it looks.

The whole idea of electrosex evolved out of medically helpful electro-therapy, where patients needing to treat muscle issues would attach electrodes to their skin, hook them up to a power box, set a timer, and let the device both contract muscles on and off and temporarily block nerve pain. The electrical pulse passes between the electrodes, stimulating the area in the middle where the current runs through. Those original medical units—TENS (Transcutaneous Electrical Nerve Stimulator) and EMS (Electro Muscle Stimulation)—can be used for e-stim, but the first commercially available model specifically for arousal, the dial-controlled analog PES Power Box, popped up in the ‘80s. The analog units are still available but tech has also taken over the fetish, and now stimmers can use digital boxes, conductive penetrables, dual boxes and even remote stimming, where someone controls another’s device remotely over the internet. Reddit user electrostim told Playboy.com there’s even a Skype user group specifically for this purpose so you can watch while you stim someone from afar.

E-stim setups can be quite elaborate, with wired labia clips and vaginal probes for women that pulse and contract muscles, or anal inserts for men.

“You can control such a wide range of feelings and sensations with electro stimulation,” said Reddit user medfetfan. “You can illicit sensations that are akin to a variable-speed vibrator, a rolling wave, stroking, tapping, sucking and pulling that are completely variable in intensity. This opens up the ability to fully customize your pleasure and be completely at its or someone else’s mercy. The sensation can feel fully enveloping because your genitals become the pathway of stimulation between two electrodes.”

Another plus? Edging. Unlike the fallible human hand, e-stim machines don’t get tired or screw up their rhythm. So you can get just to the edge of an orgasm over… and over… and over… all day long until slamming it out at the end of the night. Machine Whisperer, a 42-year-old stimmer from Ireland who chose not to use their real name for privacy, considers it giving yourself over to the machine and losing control. You’re just taken to orgasm, and there’s nothing you can do to stop it. And, with the right combination of electrodes, power supply and settings, you can get there without ever even touching yourself—a sensation electrostim says produces an orgasm about 10 times more intense than one without a charge.

E-stim setups can be quite elaborate, with wired labia clips and vaginal probes for women that pulse and contract muscles, or anal inserts for men that 23-year-old Okashii Person (not his real name) from Japan says stimulate the prostate and contract the pelvic floor. Typically though, the setup for men has two conductive silicone loops, one that goes at the head of the penis and one that goes at the base, to create sensations throughout the entirety of the shaft. For women, it’s usually one electrode on either side of the clit, or one electrode on the hood transmitting electricity to a vaginal probe.

Stimmers around the world readily admit that the market for e-stim setups is flooded with junk: cheap electrodes with bad contact, intentionally mislabeled overpriced units with limited uses, and deliberate misinformation.

“If you buy junk, you are not going to get what e-stim feels like, and you are going to be turned off to it,” electrostim said. So buy from a quality company. Stimmers recommend Erostek as the best boxes and PES Electro and E-Stim Systems for the best electrodes and penetrables.

Some stimmers (at least those with electrical knowledge) make their own boxes as well. These are built with stereo speakers and amplifiers and wired to turn audio files into electric stimulation. Basically, hook it up to an iPod or some other audio source, play a song, and experience a whole range of different sensations based on what happens in the track.

“You can go from simple sound files that make a single feeling all the way through to multi-hour symphonies of sensation all dictated by the person composing the track,” medfetfan said. “Want a slow sensuous tease? No problem. Want a track with sharp unexpected spikes and long, hard stimulation sessions? You can do that. The relative volume of the track will affect the intensity of the stimulation for the person on the other end.”

Just remember, safety first. Especially with the DIY boxes, those require serious electrical capabilities to make something safe and painless. Bad electrodes can cause hot spots, or sharp stinging sensations, where there’s only partial connection to the skin. The e-stim learning curve can be steep, but the experience—when done properly—is worth it for a feeling like none other. Some experienced stimmers may pass a charge from nipple to nipple, but the overwhelming advice says to stay below the waist. The electricity is minimal, less than what it takes to light a tiny bulb electrostim says, but it’s essentially the same current as a defibrillator. And you don’t want that going near a healthy heart—which is basically a muscle that responds to electrical impulses.

“[It] interferes with the natural rhythm,” Person said. “I wouldn’t want to accidentally shock [my boyfriend’s] heart out of rhythm. As long as people keep their toys below the chest, or the electricity doesn’t pass through your chest, there’s really no harm.”

So don’t even hold one electrode and put the other down below. The current will flow up your arm, down through your chest and then into your crotch. Unfortunately, this also means those with heart conditions or pacemakers should probably steer clear of e-stim. No sense poking an already angry tiger. Otherwise, go crazy.

“When I show someone e-stim [who] doesn’t understand it, their first response is ‘ouch’ or ‘eww you’re shocking your junk,’” electrostim said. “Most peoples’ experience with electricity is bad, like a shock or something. But e-stim is just stimulation. Sure, you can make it hurt. But that’s generally not the idea.”