The term delay line
has multiple meanings:
- In electronics and derivative fields such as telecommunications, a delay line is a device where the input signal reaches the output of the device after a known period of time has elapsed. It is rigorously defined as a single-input-channel device, 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. (The delay line may have additional taps yielding output channels with values less than n.) Specific devices and approaches:
- In Optics : cavity delay lines or trombone delay lines e.g.
- In sound reinforcement, delay lines refer to systems of additional loudspeakers used to supplement the main loudspeaker system in areas where it does not reach effectively, such as the back of a large (deep) room or underneath a balcony. The delay line loudspeakers are sent a signal that has been delayed by an amount of time corresponding to the speed of sound in air over the distances involved, roughly one millisecond per foot or 3 ms per meter.
- In neurobiology, delay lines can refer to neurons, the cells that transmit electrical information in the brain. Electrical conduction in neurons is not instantaneous; it is delayed depending on the length of the axon and other properties of the neuron (e.g. myelination). This delay can be used for time sensitive calculations; the canonical example is the calculation of inter-aural time differences in the pons, used for sound localization.
An earlier version of this page came from Federal Standard 1037C and from MIL-STD-188.