Power failure indicator

Claim 1

A BISTABLE CIRCUIT COMPRISING A LINE-OPERATED DIRECTCURRENT POWER-SUPPLY HAVING OUTPUT TERMINALS, A PAIR OF SERIALLY CONNECTED GASEOUS DISCHARGE TUBES, A RESISTOR CONNECTED IN SHUNT WITH EACH OF SAID DISCHARGE TUBES, CURRENT LIMITING MEANS CONNECTED BETWEEN ONE OUTPUT TERMINAL OF SAID POWER SUPPLY AND ONE OF SAID DISCHARGE TUBES, MEANS CONNECTING THE OTHER OF SAID DISCHARGE TUBES TO THE OTHER OUTPUT TERMINAL OF SAID POWER SUPPLY, A MANUALLY OPERATED SINGLE POLE SWITCH HAVING NORMALLY OPEN AND NORMALLY CLOSED CONTACTS, MEANS CONNECTING THE POLE OF SAID SWITCH TO THE COMMON CONNECTION OF SAID CURRENT LIMITING MEANS AND SAID ONE DISCHARGE TUBE, MEANS INCLUDING SAID NORMALLY OPEN CONTACT AND RESPONSIVE TO THE ACTUATION OF SAID SWITCH TO DECREASE THE RESISTANCE IN SHUNT WITH SAID ONE DISCHARGE, A VOLTAGE DIVIDER HAVING AN OUTPUT TERMINAL, SAID VOLTAGE DIVIDER CONNECTED BETWEEN SAID OTHER TERMINAL OF SAID POWER SUPPLY AND GROUND, ANOTHER GLOW DISCHARGE TUBE HAVING LOWER STARTING AND SUSTAINING CHARACTERISTIC VOLTAGES THAT EACH OF SAID SERIALLY CONNECTED DISCHARGE TUBES, SAID OTHER DISCHARGE TUBE BEING CONNECTED BETWEEN THE OUTPUT TERMINAL OF SAID VOLTAGE DIVIDER AND THE SAID NORMALLY CLOSED CONTACT, AND MEANS TO DERIVE AN OUTPUT SIGNAL FROM ONE OF THE DISCHARGE TUBES.