The present invention provides systems, methods and devices for selectively firing a gun train formed of a plurality of guns. Conventionally, the guns each include a detonator assembly that detonates upon receiving a firing signal transmitted by a surface source. In one embodiment of the present invention, an operator provided in the gun train selectively couples one or more of the guns to the signal transmission medium. The operator has an safe state wherein the operator isolates the gun from the firing signal and an armed state wherein the operator enable the transmission of the firing signal to the gun. A control signal is used to move operator between the safe state and the armed state. In some embodiments, two or more guns are each provided with a separate operator. In other embodiments, one operator can selectively engage two or more guns.