By adding constant-amplitude pulses to a noisy bistable system, we enhance
its response to monochromatic signals, significantly magnifying its unpulse
d stochastic resonance. We observe the enhancement in both numerical simula
tions and in analog electronic experiments, This simple noninvasive control
technique should be especially useful in noisy bistable systems that are d
ifficult or impossible to modify internally. (C) 2000 Elsevier Science B.V.
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