1. A fuze for exploding projectiles and the like in proximity to a target, comprising, means for generating radio frequency waves, means for propagating said generated waves through the space intervening between the projectile and the target, a portion of said propagated waves being reflected back by said target toward said propagation means, means connected to said propagation means for simultaneously detecting said generated waves and said reflected waves to provide a signal for firing said fuze, said detecting means being sensitive to said reflected waves only in the presence of said generated waves, a variable impedance connected to said wave generating means, and means for varying said impedance from a relatively high value to a relatively low value thereby terminating the operation of said wave generating means to render said detecting means insensitive both to reflected waves and to spurious waves.
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