Editing Line card (section)

{{Short description|Modular circuit component}}
{{Multiple image
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 | image1    = WE500GLineCard.png
 | caption1  = A [[Western Electric]] 400G line card for 1A2 key systems
 | width1    = 170
 | image2    = Northern Telecom World Line Card NT6X17BA.jpg
 | caption2  = Northern Telecom World Line Card NT6X17BA, circa 1995
 | width2    = 134
}}

A '''line card''' or '''digital line card''' is a [[modular design|modular]] [[electronic circuit]] designed to fit on a separate [[printed circuit board]] (PCB) and interface with a [[telecommunications]] [[access network]].<ref>{{cite web|url=https://www.pcmag.com/encyclopedia/term/46105/line-card |title=line card Definition from PC Magazine Encyclopedia |publisher=Pcmag.com |date= |accessdate=2014-02-19}}</ref>

A line card typically interfaces with a [[twisted pair]] cable of a [[plain old telephone service]] (POTS) [[local loop]] to the [[public switched telephone network]] (PSTN).  [[Telephone line]] cards perform multiple tasks, such as [[analog-to-digital converter|analog-to-digital]] and [[digital-to-analog converter|digital-to-analog]] conversion of voice, [[off-hook]] detection, ring supervision, line integrity tests, and other [[BORSCHT]] functions.  In some [[telephone exchange]] designs, the line cards generate [[ringing (telephony)|ringing]] current and decode [[DTMF]] signals.  The line card in a [[Subscriber Loop Carrier|subscriber loop carrier]] is called a '''subscriber line interface card''' (SLIC).<ref>{{cite web|url=http://www.cscprinters.com/line-card.html |title=Line Card |publisher=Cscprinters.com |date= |accessdate=2014-02-19}}</ref><ref name="techtarget">{{cite web|url=http://searchitchannel.techtarget.com/definition/line-card |title=What is line card? - Definition from WhatIs.com |publisher=Searchitchannel.techtarget.com |date= |accessdate=2014-02-19}}</ref>

A line card can terminate a line supporting voice [[Plain old telephone service|POTS]] service, [[ISDN]] service, [[DSL]] service, or proprietary ones. Some line cards are capable of terminating more than one type of service.<ref name="techtarget" />

Since an access [[network element]] is usually intended to interface many users (typically a few thousand), some exchanges have multiple line terminations per card. Likewise, one [[network element]] can have  many line cards.