Editing Transmission line (section)

====Star quad====
{{Main|Star quad cable}}
Star quad is a four-conductor cable in which all four conductors are twisted together around the cable axis.  It is sometimes used for two circuits, such as [[4-wire]] telephony and other telecommunications applications.  In this configuration each pair uses two non-adjacent conductors.  Other times it is used for a single, [[balanced line]], such as audio applications and [[2-wire]] telephony.  In this configuration two non-adjacent conductors are terminated together at both ends of the cable, and the other two conductors are also terminated together.

When used for two circuits, crosstalk is reduced relative to cables with two separate twisted pairs.

When used for a single, [[balanced line]], magnetic interference picked up by the cable arrives as a virtually perfect common mode signal, which is easily removed by coupling transformers.

The combined benefits of twisting, balanced signalling, and quadrupole pattern give outstanding noise immunity, especially advantageous for low signal level applications such as microphone cables, even when installed very close to a power cable.<ref>''[http://www.canare.com/UploadedDocuments/A%20Technical%20Paper%20-%20Evaluating%20Microphone%20Cable%20Perfrmance%20and%20Specifications.pdf Evaluating Microphone Cable Performance & Specifications] {{Webarchive|url=https://web.archive.org/web/20160509154052/http://www.canare.com/UploadedDocuments/A%20Technical%20Paper%20-%20Evaluating%20Microphone%20Cable%20Perfrmance%20and%20Specifications.pdf |date=2016-05-09 }}''</ref><ref>''[http://www.belden.com/blog/broadcastav/How-Starquad-Works.cfm How Starquad Works] {{Webarchive|url=https://web.archive.org/web/20161112081214/http://www.belden.com/blog/broadcastav/How-Starquad-Works.cfm |date=2016-11-12 }}''</ref> The disadvantage is that star quad, in combining two conductors, typically has double the capacitance of similar two-conductor twisted and shielded audio cable. High capacitance causes increasing distortion and greater loss of high frequencies as distance increases.<ref>{{cite book|last=Lampen|first=Stephen H.|title=Audio/Video Cable Installer's Pocket Guide|year=2002|publisher=McGraw-Hill|isbn=978-0071386210|pages=32, 110, 112}}</ref><ref>{{cite book|last=Rayburn|first=Ray|title=Eargle's The Microphone Book: From Mono to Stereo to Surround – A Guide to Microphone Design and Application|url=https://archive.org/details/earglesmicrophon00rayb|url-access=limited|edition=3|year=2011|publisher=Focal Press|isbn=978-0240820750|pages=[https://archive.org/details/earglesmicrophon00rayb/page/n168 164]–166}}</ref>