Low-current alarm for cathodic protection units

Claim 1

AN APPARATUS FOR MONITORING AN ELECTRICAL CIRCUIT COMPRISING: (A) A GALVANOMETER TYPE METER RELAY HAVING A SET OF CONTACTS, A SENSITIVE COIL AND A LOCKING COIL CONNECTED IN CIRCUIT WITH SAID CONTACTS, SAID LOCKING COIL BEING OPERABLE TO ADD A CONTACT-CLOSING FORCE TO THAT OF THE SENSITIVE COIL; (B) CIRCUIT MEANS COUPLED TO SAID SENSITIVE COIL FIR SUPPLYING A CURRENT REPRESENTATIVE OF THE ELECTRICAL CURRENT BEING MONITORED BY SAID APPARATUS; (C) A LOAD RELAY HAVING A COIL AND CONTACTS, A POWER SUPPLY COUPLED TO THE COIL OF S AID LOAD RELAY TO NORMALLY ENERGIZE SAID LOAD RELAY, THE COIL OF SAID LOAD RELAY IN ADDITION BEING COUPLED TO ONE OF THE CONTACTS TO SAID METER RELAY; (D) SAID POWER SUPPLY IN ADDITION BEING COUPLED TO THE OTHER OF THE CONTACTS OF SAID METER RELAY, THE CONTACTS OF SAID METER RELAY BEING DISPOSED TO SHORT-CIRCUIT THE COIL OF SAID RELAY BEING THROUGH THE LOCKING COIL WHEN THE CONTACTS OF SAID METER RELAY CLOSE; (E) AN INTERRUPTING RELAY HAVING A COIL AND CONTACTS, A SOURCE OF POWER, ONE SIDE OF SAID SOURCE OF POWER BEING COUPLED TO THE CONTACTS OF SAID INTERRUPTING RELAY THE OTHER SIDE OF SAID SOURCE OF POWER BEING COUPLED TO GROUND, THE CONTACTS OF SAID INTERRUPTING RELAY IN ADDITION BEING COUPLED TO THE NORMALLY CLOSED CONTACTS OF SAID LOAD RELAY, ONE SIDE OF THE COIL OF SAID INTERRUPTING RELAY BEING COUPLED TO THE NORMALLY OPEN CONTACTS OF SAID LOAD RELAY, THE OTHER SIDE OF THE COIL OF SAID INTERRUPTING RELAY BEING COUPLED TO GROUND; AND (F) AN INDICATING DEVICE COUPLED TO THE NORMALLY CLOSED CONTACTS OF SAID LOAD RELAY AND TO GROUND WHEREBY SAID LOAD RELAY WILL SUPPLY POWER TO SAID INDICATING DEVICE WHEN SAID LOAD RELAY IS ENERGIZED AND INTERRUPTED SAID SUPPLY OF POWER WHEN SAID LOAD RELAY IS SHORTED.

Claim 2

AN APPARATUS FOR MONITORING AN ELECTRICAL CIRCUIT COMPRISING: (A) A GALVANOMETER TYPE METER RELAY HAVING A SET OF CONTACTS, A SENSITIVE COIL AND A LOCKING COIL CONNECTED IN CIRCUIT WITH SAID CONTACTS, SAID LOCKING COIL BEING OPERABLE TO ADD A CONTACT-CLOSING FORCE TO THAT OF THE SENSITIVE COIL; (B) CIRCUIT MEANS COUPLED TO SAID SENSITIVE COIL FIR SUPPLYING A CURRENT REPRESENTATIVE OF THE ELECTRICAL CURRENT BEING MONITORED BY SAID APPARATUS; (C) A LOAD RELAY HAVING A COIL AND CONTACTS, A POWER SUPPLY COUPLED TO THE COIL OF S AID LOAD RELAY TO NORMALLY ENERGIZE SAID LOAD RELAY, THE COIL OF SAID LOAD RELAY IN ADDITION BEING COUPLED TO ONE OF THE CONTACTS TO SAID METER RELAY; (D) SAID POWER SUPPLY IN ADDITION BEING COUPLED TO THE OTHER OF THE CONTACTS OF SAID METER RELAY, THE CONTACTS OF SAID METER RELAY BEING DISPOSED TO SHORT-CIRCUIT THE COIL OF SAID RELAY BEING THROUGH THE LOCKING COIL WHEN THE CONTACTS OF SAID METER RELAY CLOSE; (E) AN INTERRUPTING RELAY HAVING A COIL AND CONTACTS, A SOURCE OF POWER, ONE SIDE OF SAID SOURCE OF POWER BEING COUPLED TO THE CONTACTS OF SAID INTERRUPTING RELAY THE OTHER SIDE OF SAID SOURCE OF POWER BEING COUPLED TO GROUND, THE CONTACTS OF SAID INTERRUPTING RELAY IN ADDITION BEING COUPLED TO THE NORMALLY CLOSED CONTACTS OF SAID LOAD RELAY, ONE SIDE OF THE COIL OF SAID INTERRUPTING RELAY BEING COUPLED TO THE NORMALLY OPEN CONTACTS OF SAID LOAD RELAY, THE OTHER SIDE OF THE COIL OF SAID INTERRUPTING RELAY BEING COUPLED TO GROUND; AND (F) AN INDICATING DEVICE COUPLED TO THE NORMALLY CLOSED CONTACTS OF SAID LOAD RELAY AND TO GROUND WHEREBY SAID LOAD RELAY WILL SUPPLY POWER TO SAID INDICATING DEVICE WHEN SAID LOAD RELAY IS ENERGIZED AND INTERRUPTED SAID SUPPLY OF POWER WHEN SAID LOAD RELAY IS SHORTED.