Abstract. Аsynchronous threshold element is an element with several inputs and one output, which can be in two states, active and passive. When active, it generates a signal of a certain power. The state of an element is determined by the value of its potential: if the potential exceeds the threshold, the element is active. Other parameters of the element are the input weights and two endogenous rates of potential change: for the active and passive states. The total rate of change in the potential of an element depends on the input signals and endogenous rates. An element is called reactive if both of its endogenous rates are negative. It is activated only when there are sufficiently strong input signals. A chain of asynchronous elements is a network of elements N1, ..., Nn, in which a single output of Niis connected to a single input of Ni+1. It is shown that even in the case where the elements are homogeneous (have the same parameters), the external signal that activates N1 may not reach Nn. The necessary and sufficient conditions for the signal to pass through the entire chain are given.