The CBS-4 is a multipoint earth leakage relay: one unit that monitors and protects four separate circuits independently, each through its own external toroidal transformer of the Circutor WG/WGC range. Circutor's own title for the family, in the instruction manual, is "Multipoint earth leakage relay". It carries five output relays — four to trip the circuit breaker of each protected channel, and one further relay for the pre-alarm and maintenance function, which is what lets a developing insulation fault be found and repaired before it trips anything. Sensitivity is adjustable from 30 mA to 30 A and the tripping delay from 0.02 to 10 seconds, per channel, and the unit is fully programmable and suitable for all neutral earthing arrangements — TT, TN and IT. It occupies three DIN modules and runs from a 230 V AC supply. 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 CBS-4. Supplied by cBallast on quote-to-invoice terms; lead time and freight are quoted per RFQ against the destination Incoterm.