The words used in e-stim come from electronics, medicine and hobby slang, and makers don't always agree on them. This list gives the everyday meaning of each, with a link to the article that covers it properly.
A to C#
Adaptation: the way a sensation fades when the same pulses repeat for a while, as the nerves get used to them. The reason units have changing modes.
Amplitude: the strength of each pulse. Usually labelled level, intensity or power on the unit.
Balanced pulse: a biphasic pulse whose two halves carry equal charge, so nothing builds up in the skin. Also called symmetrical or charge-balanced.
Banana plug: a sprung plug, 4 mm across, used on many purpose-made electrodes. See Cables and Connectors.
Biphasic: a pulse that goes one way and then the other. See Pulses, Frequency and Waveforms.
Bipolar electrode: one item with two separate contacts, which completes the circuit on its own. See Electrode Types.
Burst: a mode that sends groups of pulses with pauses between them.
Channel: one output of a unit, with two connections and its own level control.
Conductive gel: a water-based gel that fills the gaps between an electrode and the skin. See Conductive Gel and Lubricant.
Conductive rubber: rubber or silicone loaded with carbon so that it carries current. Used for loops, bands and flexible electrodes.
Contraindication: a medical reason not to use something, such as a pacemaker. See E-Stim Safety.
Current: the flow of electricity, measured in amps. E-stim uses thousandths of an amp (milliamps, mA). Current is what you feel.
Current density: current divided by the area it passes through. High current density is what stings and burns. See Contact Area and Current Density.
D to M#
Duty cycle: the share of the time the output is on. In EMS, usually the work and rest times of a contraction programme.
Electrode: the part that touches the body and passes the current to it.
EMS: electrical muscle stimulation. Units designed to make muscles contract. Also called NMES. See TENS, EMS and E-Stim Units.
Frequency: how many pulses are sent each second, in hertz (Hz). Also called pulse rate.
Hertz (Hz): one per second. 50 Hz means fifty pulses every second.
Intensity: see Amplitude.
Isolation: having no electrical connection to the mains or to earth. See Batteries, Chargers and Mains Power.
Jack plug: the round plug used on headphones. E-stim leads commonly use 3.5 mm or 2.5 mm sizes at the unit end.
Lead: the cable from the unit to the electrodes.
Microsecond (µs): a millionth of a second. The unit for pulse width.
Milliamp (mA): a thousandth of an amp.
Mode: a preset pattern of pulses. Also called a programme or routine.
Modulation: changing the level, rate or width over time to make a pattern.
Monophasic: a pulse that only ever goes one way.
Monopolar electrode: an electrode with a single contact. It needs a second electrode on the same channel to complete the circuit.
N to Z#
NMES: neuromuscular electrical stimulation. Another name for EMS.
Open circuit: a break in the loop, such as an electrode that has come off. No current flows.
Pad: a flat electrode, usually self-adhesive.
Pigtail: the short wire attached to a pad, ending in a socket for a 2 mm pin.
Polarity: which of a channel's two connections is which. It only matters when the pulses are unbalanced.
Power box: common name for a purpose-made e-stim unit. Also control box or power unit.
Pulse: one short burst of current. E-stim is a stream of them.
Pulse rate: see Frequency.
Pulse width: how long each pulse lasts, in microseconds. Longer feels stronger and deeper. Also called pulse duration.
Ramp: a gradual rise or fall in level. A soft start is a ramp up.
Resistance: how much something opposes current, measured in ohms. Dry skin has a high resistance, and wet or broken skin a low one.
Short circuit: an unintended direct path, such as two electrodes touching, that lets current bypass the body.
Snap: a press-stud connector on some pads.
Splitter: a lead that divides one channel between more than one pair of electrodes.
Stereostim: driving a two-channel output from the left and right channels of a stereo audio signal. See Audio-Driven E-Stim.
TENS: transcutaneous electrical nerve stimulation. Units designed for pain relief through the skin.
Threshold: the lowest level at which you can first feel the output.
Tri-phase: an arrangement where two channels share a common electrode, so the sensation shifts between three contacts. Only for units that are designed for it.
Voltage: the electrical "pressure" that pushes current through a resistance, measured in volts.
Waveform: the shape of the output over time: the pulses' shape, size and spacing taken together.