On the delay time of the total signal from a set of transmitters

The time dependence of the total signal from a group of closely spaced acoustic or electromagnetic transmitters radiating the same (up to an amplitude factor) signals is considered. If the duration of the partial signal is sufficiently long, the time dependence of the signal from the set of transmitters turns out to be close to that of the signal from a single transmitter up to a delay time. This delay does not necessarily coincide with the time it takes for an optical (or acoustic) signal to pass from the transmitters to the observation point. At different points of the space, this delay time may exceed, or be shorter than, the light (sound) delay time and also may be positive or negative. This follows from the backward or forward extrapolation of the time dependence of the signal when variously delayed and attenuated copies of the same signal that are produced by different transmitters are added up (i.e., interfere). One result of such an extrapolation, which arises upon transmitting a signal with its leading or trailing edge cut off, is the reconstruction of its time dependence, i.e., the detection of the nontransmitted part of the signal.