The first device that used this principle was the Perceptron. This machine was constructed at the NPL in the 'GOs.
Nerves have many inputs called dendrites and an output called an axon.
The probability that the all or nothing output will be fired depends on the degree of excitation arriving along the dendrites. These resistors were connected to photocells arranged in a square array. Each photocell was connected to every schmitt trigger through the variable resistors. The firing of a particular trigger depended on the setting of the resistors and the degree of illumination of Lhe photocells. To program the device the resistors had to be altered until the correct response was produced.