Long interval timing circuit

Claim 1

A long time interval heavy direct current device for automotive use actuatable by a pushbutton pulse-type switch in the ignition circuit and comprising; a load terminal, a battery terminal, an actuating switch terminal and a chassis ground connection, a single relay having a first relay winding, a second bucking winding and normally open contacts; a timing resistor and polarized charging condenser in series between the battery terminal and ground through said normally open contacts; a holding resistor between said load terminal and said switch terminal and said ground connection; a transistor having an anode connected between said timing resistor and condenser; voltage dividing resistor in series between said load terminal and said ground connection, said transistor having a gate connected between said voltage dividing resistors to determine the voltage at which said condenser discharges through said transistor, said transistor having a cathode connecting through said bucking winding in opposition to said first winding with said condenser discharge thus to open the contacts of said relay after a period of time determined substantially by said timing resistor and said condenser, the holding resistor forming a part of the circuit sealing in actuation of the first relay winding after actuation of the pushbutton pulse type resistor.