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A system for selectively actuating multiple load devices, such as well tools, which are selectively actuated by applying a predetermined voltage across a predetermined pair of conductors. At least one lockout device is associated with each load device. The lockout device prevents current from flowin

A system for selectively actuating multiple load devices, such as well tools, which are selectively actuated by applying a predetermined voltage across a predetermined pair of conductors. At least one lockout device is associated with each load device. The lockout device prevents current from flowing through the respective load device until voltage across the pair of the conductors exceeds a predetermined minimum. A method is provided for selecting well tools for actuation by applying a minimum voltage across a set of conductors and a lockout device. Leak paths are prevented from draining off current by the lockout devices. A system is provided for applying current to bidirectional load devices such as downhole pumps and motors.

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1. A system for selectively actuating from a remote location multiple downhole well tools in a well, the system comprising: at least one load device associated with each of the well tools, such that a particular one of the well tools can be actuated when the corresponding load device is actuated;con

1. A system for selectively actuating from a remote location multiple downhole well tools in a well, the system comprising: at least one load device associated with each of the well tools, such that a particular one of the well tools can be actuated when the corresponding load device is actuated;conductors connected to the load devices, whereby each of the load devices can be actuated by applying a predetermined voltage potential across a respective predetermined pair of the conductors; anda lockout device for each of the load devices, whereby each lockout device prevents current from flowing through the corresponding load device if the voltage potential across the respective predetermined pair of the conductors is less than a predetermined minimum; andwherein each of the lockout devices includes an silicon controlled rectifier (SCR), a pair of resistors and a gate, and wherein the SCR is actuated only where the voltage applied across the lockout device exceeds a predetermined minimum gate voltage. 2. The system of claim 1, wherein the predetermined voltage minimum is the breakdown voltage of the SCR. 3. The system of claim 1, wherein the load devices are bidirectional load devices, and wherein the lockout devices are selected from the group consisting of: DIACs, SIDACs, TRIACs, and SCRs. 4. The system of claim 3, wherein each bidirectional load device has a corresponding pair of lockout devices arranged in parallel. 5. A method of selectively actuating from a remote location multiple downhole load devices in a well, the method comprising the steps of: selecting a first one of the load devices for actuation by applying a predetermined minimum voltage potential to a first set of conductors in the well; andpreventing leakage along at least one current leak path, at least one of the leak paths through at least one other conductor and at least one other load device, by positioning a lockout device along the leak path, the lockout device preventing current from flowing through the corresponding load device if the voltage potential across the lockout device is less than a predetermined minimum;wherein the selecting step further comprises permitting current flow through the first load device in response to applying the predetermined minimum voltage potential across a lockout device interconnected between the first load device and the first set of conductors; andwherein the step of current flow permitting further comprises applying a voltage greater than the breakdown voltage of the lockout device. 6. A system for selectively actuating from a remote location multiple downhole bidirectional load devices in a well, the system comprising: a direct current power supply;a plurality of bidirectional load devices positioned in a well;a plurality of conductors connected to the power supply and the bidirectional load devices, whereby each of the bidirectional load devices can be actuated by applying a voltage potential across a respective predetermined pair of the conductors, and whereby each of the bidirectional load devices can be run forward or backward depending on the direction of current through the pair of conductors; andat least one lockout device connected to each bidirectional load device, whereby the lockout device prevents current from flowing through the corresponding bidirectional load device until the voltage potential across the lockout device exceeds a predetermined minimum;wherein the at least one lockout device connected to each bidirectional load device further comprises: a pair of lockout devices, arranged in parallel, and each connected to the corresponding bidirectional load device, wherein each lockout device prevents current flow in a selected direction, and wherein each lockout device prevents current flow therethrough until the voltage potential across the lockout device exceeds a predetermined minimum. 7. A system as in claim 6, wherein the lockout devices are selected from the group consisting of: thyristors, SCRs, DIACs, SIDACs, and TRIACs. 8. A system as in claim 6, wherein the bidirectional load devices are selected from the group consisting of: motors and pumps. 9. A system as in claim 6, wherein the at least one lockout device comprises: a bidirectional lockout device, connected to the corresponding bidirectional load device, wherein the bidirectional lockout device prevents current flow in either direction, and wherein each lockout device prevents current flow therethrough until a voltage potential across the lockout device exceeds a predetermined minimum. 10. A system as in claim 9, wherein the bidirectional lockout device is selected from the group consisting of: DIACs, diactors, and TRIACs.