E-Stim Machine

Originally adapted from electric devices used in medical settings such as Electronic Muscle Stimulation (EMS) and transcutaneous electrical nerve stimulation (TENS) machines. E-Stim machines are more specialized for kink activities.

The device is used to control muscle movement of the recipient, but also to give them painful stimulation. Due to the customization options of the device this can go from softly teasing to full overload in stimulation. Also using the device on different parts of the body will have different effects depending on the recipient.

Generally devices use pulsating DC or AC currents between two electrodes. Many devices will have an option to add more than 1 pair of electrodes and you will always have a positive and a negative side. The central electrical unit can work based on batteries, but there are also versions that are connected by a mains power cable..

The electrodes are often re-usable stickers that can be put on the body, however for kink there are also alternative attachments. Common are nipple clamps, buttplugs or dildos. But with imagination the only limit is how conductive the material is and so pinwheels, floggers and other items can be converted into electrodes.

Variation in control units

The control units are to be found in a wide price and functionality range. A basic unit is fairly cheap, but it can go all the way to computer controlled and programmable units that cost a couple of hundred bucks.

The difference in function they often have is how powerful they are, and what kind of capabilities they have to control frequency of pulses and AC vs DC which can apply different kinds of stimulation. It is often advised to start with a lower end model and see if it is interesting, if so there are options to grow with.

Risks

Note that the use of a device like this, even with the lower level of electric involved does put a strain on the body. For EMS it is advised to only use it 1-2 times a week (source).

Additionally if you're using DC currents through a body, it's okay for some parts of the body, but not for others. AC currents also have their risks on certain areas on the body. It is generally advised that you make sure to avoid putting electrodes on opposite sides of vital organs.

Many of the devices you can buy online may look fully tested, but not all are properly certified, due to the nature of the sex industry. So be careful and look for reputable brands that have good reviews for their products.