Patent ID: 8590609

Claim:
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; and a 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; and wherein 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.