The RGU-10 is a programmable electronic earth leakage relay for use with an external toroidal transformer of the Circutor WG/WGC range, which is ordered separately and sized to the cable it encircles. An earth leakage relay does not break the circuit itself. It measures the residual current — the difference between the current flowing out to a load and the current returning from it, which is only non-zero when some of it is escaping to earth — and signals a separate switching device to open. That split is what allows it to protect circuits far larger than any self-contained RCD can handle, and to be set for sensitivity and time delay independently of the breaker it drives. Sensitivity is adjustable from 30 mA to 30 A and the trip delay from 0.02 to 10 seconds, which together let the device be set for genuine selectivity against RCDs downstream of it. It provides two independently programmable outputs — a main trip and a pre-alarm — and an external 230 V AC input for remote reset and remote test. It occupies three DIN modules, runs from 230 V AC, is fully programmable and suits all neutral earthing arrangements: TT, TN and IT. It is a type A device: it responds to sinusoidal AC residual currents and to pulsating DC residual currents. Circutor specify it as superimmunised, with high-frequency filtering and true RMS (TRMS) measurement, so that the harmonic leakage normal in an installation full of switch-mode loads does not read as a fault. Manufactured by Circutor (Spain) and supplied under the Function brand; the Circutor catalogue reference is RGU-10. Supplied by cBallast on quote-to-invoice terms; lead time and freight are quoted per RFQ against the destination Incoterm.