Helicopter warning system

Claim 1

IN A WARNING SYSTEM COMPRISING, IN COMBINATION; AN ALARM CIRCUIT INCLUDING SWITCH MEANS ADAPTED FOR DISPOSITION IN DORMANT AND SIGNALING CONDITIONS; GATE MEANS HAVING A SIGNAL OUTPUT FOR DETERMINING THE CONDITION OF SAID SWTICH MEANS; FIRST AND SECOND PULSE NETWORKS CONNECTED TO SAID GATE MEANS AND ADAPTED TO ALTER THE SIGNAL OUTPUT OF SAID GATE MEANS IN ACCORD WITH COINCIDENCE OF SIGNALS FROM SUCH NETWORKS; AC SIGNAL GENERATING MEANS ADAPTED FOR CONNECTION TO THE MECHANISM BEING MONITORED; A FIXED DELAY CIRCUIT CONNECTED TO SAID AC SIGNAL GENERATING MEANS AND HAVING ITS OUTPUT CONNECTED TO SAID FIRST PULSE NETWORK; A FREQUENCY VARIABLE DELAY CIRCUIT CONNECTED TO SAID AC SIGNAL GENERATING MEANS AND HAVING ITS OUTPUT CONNECTED TO SAID SECOND PULSE NETWORK, SAID FREQUENCY VARIABLE DELAY CIRCUIT COMPRISING AN LC PHASE SHIFTING CIRCUIT CONNECTED TO THE AC SIGNAL GENERATING MEANS, A PULSE FORMING CIRCUIT CONNECTED TO THE PHASE SHIFTING CIRCUIT AND HAVING A POSITIVE PULSE OUTPUT IN WHICH THE TRAILING EDGES OF THE POSITIVE PULSES COINCIDE WITH POSITIVE PEAK VOLTAGES OF THE AC SIGNAL GENERATING INPUT, A PULSE AMPLIFIER, AND A DIFFERENTIATING CIRCUIT CONNECTING THE PULSE FORMING CIRCUIT TO THE AMPLIFIER, SAID AMPLIFIER BEING BIASED TO RESPOND ONLY TO NEGATIVE-GOING INPUT PULSES THERETO.