Editing Trunking (section)

==Telecommunications==
A trunk line is a [[Electrical network|circuit]] connecting [[telephone switchboard]]s (or other switching equipment), as distinguished from [[local loop]] circuit which extends from [[telephone exchange]] switching equipment to individual [[telephones]] or information origination/termination equipment.<ref>{{FS1037C MS188}}</ref><ref>[[Title 47 of the Code of Federal Regulations]], Parts 0-199</ref>

Trunk lines are used for connecting a [[private branch exchange]] (PBX) to a telephone service provider.<ref>{{cite web |website=Versadial.com |url=https://www.versadial.com/faqs/definitions-common-call-recording-terms |title=Call Recording Terms/Definitions |access-date=8 June 2015 }}</ref> When needed they can be used by any telephone connected to the PBX, while the station lines to the [[Extension (telephone)|extensions]] serve only one station’s telephones. Trunking saves cost, because there are usually fewer trunk lines than extension lines, since it is unusual in most offices to have all extension lines in use for external calls at once. Trunk lines transmit voice and data in formats such as [[Analog signal|analog]], [[Digital signal 1|T1]], [[Digital signal 1|E1]], [[ISDN]], [[Primary rate interface|PRI]] or [[SIP trunking|SIP]]. The [[dial tone]] lines for outgoing calls are called DDCO (Direct Dial Central Office) trunks.

In the UK and the Commonwealth countries, a ''trunk call'' was the term for [[long-distance calling]] which traverses one or more trunk lines and involving more than one telephone exchange. This is in contrast to making a [[local call]] which involves a single exchange and typically no trunk lines.

Trunking also refers to the connection of [[switch]]es and [[Telecommunication circuit|circuits]] within a [[telephone exchange]].<ref>{{cite book |last=Flood |first=J. E. |title=Telecommunications Switching, Traffic and Networks |chapter=Telecommunications Traffic |location=New York |publisher=Prentice-Hall |year=1998 |isbn=0130333093 }}</ref> Trunking is closely related to the concept of [[Grade of service|grading]]. Trunking allows a group of [[inlet]] switches at the same time. Thus the [[service provider]] can provide a lesser number of circuits than might otherwise be required, allowing many users to "share" a smaller number of connections and achieve capacity savings.<ref>Motorola, [http://www.motorola.com/LMPS/RNSG/trunking Trunking Communications Overview], last accessed 13 February 2005.</ref>