These taps give telephone companies some flexibility in meeting the variable demand for service.
New service is provided by connecting a bridged tap part way along an existing wire pair.
Both the length and, to a lesser degree, the placement of a bridged tap determine the effect that it will have on the signal. A portion of the signal travels down the bridged tap and is reflected off the unterminated end. If the length of the tap is small, when compared to the signal wavelength, the reflected signal rejoins the original signal after a minimal phase shift and there is little attenuation of the original signal. When the bridge tap length approaches one fourth of the signal wavelength, the reflected signal rejoins with a phase difference nearing 180 degrees and causes significant attenuation. Even if such a long tap were connected, line attenuation would make the reflected signal amplitude negligible.