Activation function binary threshold

The binary threshold activation function was used in early attempts to create ANNs because of a perceived parallel between this function and the way that neurons operate in the brain. Neurons require a certain level of activation before they will "fire," otherwise they are quiescent. A TLU functions in the same way. 

To address general questions of connectivity and function, the system is modeled with time-discrete, binary neurons (McCulloch and Pitts 1943) which fire (have value 1) whenever the sum of active, connected neurons in the previous time step is larger than their firing threshold 6,... 

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