Load coils are used to reduce attenuation on a copper pair, a condition in which the capacitance of the telephone line decreases the signal as it is transmitted over a distance. A user experiences this decrease as a loss of volume. Load coils are used in approximately 20 percent of the outside plant pairs in North America. With load coils, voice-frequency signals are passed with lower attenuation than if there were no coils present. Proper loading is critical for data transmission in Internet access and in fax, data, and other nonvoice calls.
Attenuation can be a very serious problem in transmitting voice and data.
The transmission will have some amount of loss, as a result of the resistance and capacitance of the cable. This loss is logarithmic in nature on nonloaded cable. Without load coils, the loss would be so severe that at 36,000 feet from the CO, callers would need to shout in order to communicate with each other, particularly if the transmission was at higher frequencies. It is essential that load coils be deployed correctly. If a cable splicer fails to install a load coil at an appropriate place, attenuation will take place.