Abstract: A system for initiating an action in response to a plurality of variably weighed inputs as a layered configuration, and at least two layers. The first layer has: a) sensors for receiving a plurality of first input signals; b) signal weighting units for applying a weighting to the first input signals; c) a trip device for receiving the weighted first input signals, summing the signals and being activated to produce a trip signal when the sum of the weighted first input signals reaches a predetermined threshold level; and d) a first stage unit for initiating a first active state on receiving the trip signal. The second layer has: a) a sensor for receiving a second input signal on initiation of a first active state; and b) a state unit for initiating a second active state when the second input signal reaches a predetermined threshold level. The initiation of the second active state suppresses the first active state.