Describes a circuit that is either On or Off, with either 100% or 0% power.
A source of some confusion, as the term has changed historically. Originally, stage lighting systems had dimmers, and a few non-dims that were switches or relays. With the advent of computer consoles with various dimmer profiles, one of them being "Full at 1%", any dimmer could act as a non-dim, FOR INCANDESCENT LOADS. Further muddying the waters is the ETC Sensor's CEM, which allows a dimmer circuit to be assigned as a "Non-Dim" as well as "Switched" setting. Non-dim mode is regulated voltage, Switched mode is unregulated; but in either case, the waveform is still being clipped somewhat by the SSR, and thus is not a true sinewave.
See the attached link from ETC for more: http://www.etcconnect.com/Support/Articles/Non-Dim-vs-Switched-Mode---Regulated-vs--Unregulated.aspx .
See also relay, hot pocket, and convenience outlet.