The MICRO-4 is a compact earth fault relay with adjustable sensitivity from 30 to 300 mA and a 1 second tripping delay, running from a 230 V AC supply and providing a potential-free normally-open alarm contact. An earth fault relay 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 rather than breaking the circuit itself, so it can be applied to circuits far larger than a self-contained RCD could switch and set for sensitivity independently of the device it drives. This is the version supplied WITHOUT the indicator panel, for installations where the alarm contact is taken to a control system rather than read locally. The only difference between this item and the MICRO-4 listed with a panel is the panel itself — the relay, its 30 to 300 mA adjustable range and its 1 second delay are identical. Manufactured in Spain and supplied under the Function brand. Supplied by cBallast on quote-to-invoice terms; lead time and freight are quoted per RFQ against the destination Incoterm.