For these reasons, Krarup cable was popular on shorter distances, where the distortion was not so high that loading coils had to be used, until the advent of permalloy cable superseded it.
32.
Other factors such as long loops, loading coils, pair gain, electric fences ( usually in rural locations ), and digital loop carriers can also slow connections to 20 kbit / s or lower.
33.
The stations themselves resembled a utility powerhouse, with large electric motors turning the humming alternators, which were connected through huge loading coils to enormous wire antenna systems stretching for miles, suspended on steel towers.
34.
Submarine communications cables are particularly subject to the problem, but early 20th century installations using balanced pairs were often continuously loaded with iron wire or tape rather than discretely with loading coils, which avoided the sealing problem.
35.
The test site was typical of Bell System outside plant of the time in that, to accommodate loading coils, empirically the capacity was increased until the failure rate was unacceptable, then reduced to leave a margin.
36.
Loading coils are historically also known as "'Pupin coils "'after Mihajlo Pupin, especially when used for the Heaviside condition and the process of inserting them is sometimes called " pupinization ".
37.
For frequencies lower than the longwave range, masts have to be electrically enlarged by base loading coils or structures on the top, because the heights required for masts of even a quarter wavelength are too large to realize physically.
38.
However, a real line is unlikely to meet this condition without the addition of loading coils and, furthermore, there are some frequency dependent effects operating on the primary " constants " which cause a frequency dependence of the loss.
39.
When his calculations showed that the manholes on telephone routes were sufficiently close together to be able to insert the loading coils without the expense of either having to dig up the route or lay in new cables he changed to this new plan.
40.
For example, at 30 MHz ( 10 m wavelength ) a true resonant ?wavelength monopole would be almost 2.5 meters long, and using an antenna only 1.5 meters tall would require the addition of a loading coil.
