The basic Nv neuron responds to a rising input by switching its normally high output to a low one for a varying amount of time. Given an input that goes from high to low to high again, on the low-to-high transition, the output will go from high to low. After a delay (determined by the resistor and capacitor values), the output will switch back to high. This allows you to chain Nv neurons together and have a signal travel slowly along the chain.
One essential difference is that the Nv responds immediately to an input, and sends the output for a time duration -- the delay occurs AFTER the output is sent. The Nu responds to an input after a delay and sends the output continuously -- the delay occurs BEFORE the output is sent.
