Pressure responsive pump control

Claim 1

IN COMBINATION WITH A SUMP OR THE LIKE, A PUMPOUT SYSTEM FOR MAINTAINING THE SURFACE OF LIQUID IN SAID SUMP BETWEEN PREDETERMINED LEVELS, SAID SYSTEM COMPRISING: FIRST AND SECOND MOTOR DRIVING PUMPS DISPOSED ADJACENT SAID SUMP, EACH PUMP HAVING AN INLET AND AN OUTLET; CIRCUIT MEANS INTERCONNECTING SAID PUMPS FOR OPERATIN SAID PUMPS ALTERNATELY; A SEPARATE PUMP-OUT PIPE CONNECTED TO EACH PUMP INLET AND COMMUNICATING WITH THE LIQUID IN SAID SUMP; A PRESSURE TAP CONDUIT EXTENING BETWEEN SAID PUMP-OUT PIPES AT A LOCATION OUTSIDE SAID SUMP, SAID CONDUIT PASSING LIQUID IN THE DIRECTION DETERMINED BY WHICHEVER PUMP IS OPERATING; FIRST AND SECOND PRESSURE SENSITIVE ELEMENTS FOR GENERATING A CONTROL SIGNAL FOR THE DRIVE MOTOR OF SAID FIRST AND SECOND PUMPS, RESPECTIVELY; AND GAS-FILLED CONDUIT MEANS EXTENDING FROM SAID PRESSURE SENSITIVE ELEMENTS TO A COMMON JUNCTION WITH SAID PRESSURE TAP CONDUIT, SAID JUNCTION BEING DISPOSED INTERMEDIATE THE ENDS OF SAID PRESSURE TAP LINE, WHEREBY THE LOCATIONS OF THE CONNECTIONS BETWEEN THE PRESSURE TAP LINE AND THE PUMP-OUT PIPES AND BETWEEN THE PRESSURE TAP LINE AND THE GAS-FILLED CONDUIT MEANS MAY BE SELECTED SO AS TO COMPENSATE FOR DIFFERENCES IN THE HYDRAULIC CHARACTERISTICS OF THE SETS OF PUMP AND PUMP-OUT PIPES AND TO THEREBY PROVIDE EQUAL PRESSURE SIGNALS TO SAID PRESSURE SENSITIVE ELEMENTS REGARDLESS OF WHICH PUMP IS OPERATING.