A transmission line, or equivalent device, used to delay a signal. 2. A single-input-channel device, such as a single-input sequential logic element, in which the output channel state at a given instant, t, is the same as the input channel state at the instant t-n, where n is a number of time units, i.e., the input sequence undergoes a delay of n time units, such as n femtoseconds, nanoseconds, or microseconds. Note: The delay line may have additional taps yielding output channels with values less than n.