Network interface device: Difference between revisions

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{{Short description|Device that separates the carrier's wiring from the customer's}}

{{Distinguish|Network Device Interface|Network interface controller}}

{{More footnotes needed|date=June 2010}}

[[file:Network interface device ameritech.jpg|thumb|upright|Two simple NIDs, carrying six lines each, on the outside of a building]]

[[file:apl germany.jpeg|thumb|upright|A German copper phone line termination box called ''[[:de:Abschlusspunkt Linientechnik|Abschlusspunkt LinienTechnik]]'' (APL, "[[Demarcation point]]")]]

In [[telecommunicationtelecommunications]]s, a '''network interface device''' ('''NID'''; also known by several other names) is a device that serves as the [[demarcation point]] between the carrier's [[local loop]] and the customer's [[on-premises wiring|premises wiring]]. Outdoor telephone NIDs also provide the subscriber with access to the station wiring and serve as a convenient [[test point]] for verification of loop integrity and of the subscriber's inside wiring.

== Naming ==

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A '''smartjack''' is a type of NID with capabilities beyond simple electrical connection, such as diagnostics.

An '''[[#Optical network terminals|optical network terminal]]''' (ONT) is a type of NID used with [[Fiber to the x|fiber-to-the-premises]] applications.

== Wiring termination ==

The simplest NIDs are essentially just a specialized set of wiring [[terminal (electronics)|terminal]]s. These will typically take the form of a small, weather-proof box, mounted on the outside of the building. The [[telephone line]] from the [[Telecommunications company|telephone company]] will enter the NID and be connected to one side. The customer connects their wiring to the other side. A single NID enclosure may contain termination for a single line or multiple lines.

In its role as the demarcation point (dividing line), the NID separates the telephone company's equipment from the customer's wiring and equipment. The telephone company owns the NID itself, and all wiring up to it. Anything past the NID is the customer's responsibility. To facilitate this, there is typically a test jack inside the NID. Accessing the test jack disconnects the customer premises wiring from the [[public switched telephone network]] and allows the customer to plug a "known good" [[telephone]] into the jack to isolate trouble. If the telephone works at the test jack, the problem is the customer's wiring, and the customer is responsible for repair. If the telephone does not work, the line is faulty and the telephone company is responsible for repair.

Most NIDs also include "circuit protectors", which are [[surge protector]]s for a telephone line. They protect customer wiring, equipment, and personnel from any transient [[energy]] on the line, such as from a [[lightning]] strike to a [[telephoneutility pole]].

Simple NIDs are "dumb" devices, as they contain no [[Logic gate|digital logic]]; they are "dumb" devices. They have no capabilities beyond wiring termination, circuit protection, and providing a place to connect test equipment.

== Smartjack ==

{{Main|Intelligent Network Interface Device}}

[[file:Network Interface Unit.jpg|thumb|upright|Three smartjacks for [[Digital Signal 1|T-1]] circuits, in two shelves; a [[66 block]] is on the left]]

Several types of NIDs provide more than just a terminal for the connection of wiring. Such NIDs are colloquially called ''smartjacks'' or [[Intelligent Network Interface Device]]s (INIDs) as an indication of their built-in "intelligence", as opposed to a simple NID, which is just a wiring device. Smartjacks are typically used for more complicated types of [[telecommunications service]], such as [[Digital Signal 1|T1 lines]]. [[Plain old telephone service]] lines generally cannot be equipped with smartjacks.

Despite the name, most smartjacks are much more than a simple [[Telephone jack and plug|telephone jack]]. One common form for a smartjack is a [[printed circuit board]] with a face plate on one edge, mounted in an enclosure.

Several types of NIDs provide more than just a terminal for the connection of wiring. Such NIDs are colloquially called ''smartjacks'' or [[Intelligent Network Interface Device]]s (INIDs) as an indication of their built-in "intelligence", as opposed to a simple NID, which is just a wiring device. Smartjacks are typically used for more complicated types of telecommunications service, such as [[Digital Signal 1|T1 lines]]. [[Plain old telephone service]] lines generally cannot be equipped with smartjacks.

A smartjack may provide signal conversion, converting codes and protocols, (''e.g.'', framing types), to the type needed by the customer equipment. It may buffer and/or regenerate the signal, to compensate for signal degradation from line transmission, similar to what a [[repeater]] does.

Despite the name, most smartjacks are much more than a simple [[telephone jack]]. One common form for a smartjack is a [[printed circuit board]] with a face plate on one edge, mounted in an enclosure.

A smartjack may provide signal conversion, converting codes and protocols (e.g. framing types) to the type needed by the customer equipment. It may buffer and/or regenerate the signal, to compensate for signal degradation from line transmission, similar to what a [[repeater]] does.

Smartjacks also typically provide diagnostic capabilities. A very common capability provided by a smartjack is [[loopback]], such that the signal from the telephone company is transmitted back to the telephone company. This allows the company to test the line from the central [[telephone exchange]], without the need to have test equipment at the customer site. The telephone company usually has the ability to remotely activate loopback, without even needing personnel at the customer site. When looped back, the customer equipment is disconnected from the line.

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== Optical network terminals ==

[[File:Tellabs ONT611 inside.jpeg|thumb|An optical network terminal mounted to the outside of a building, with the cover open]]

In fiber-to-the-premises systems, the signal is transmitted to the customer premises using [[optical fiber]] technologies. Unlike many conventional telephone technologies, this does not provide power for premises equipment, nor is it suitable for direct connection to customer equipment. An '''optical network terminal''' ('''ONT''', an [[ITU-T]] term), also known as an '''optical network unit''' ('''ONU''', an [[Institute of Electrical and Electronics Engineers|IEEE]] term), is used to terminate the optical fiber line, [[multiplexing|demultiplex]] the signal into its component parts (voice [[telephone]], [[television]], and [[Internet access]]), and provide power to customer telephones. If the device combines all these services into one it is known as an [[Integrated access device|IAD]]. As the ONT must derive its power from the customer premises electrical supply, many ONTs have the option for a [[Electric battery|battery]] backup in order to maintain service in the event of a [[power outage]] or it will go in alarm mode if disconnected and customer may be notified of this.<ref name="whatont" /> These terminals are used in both [[Fiber to the x#Active optical network|active optical networks]] and [[passive optical network]]s. Typically, an ONT connects via a fiber-optic cable to an [[Optical line termination|OLT]] to complete a connection. An ONT can work in Single Family Unit/SFU mode (modem/bridge) or Home Gateway Unit/HGU mode (router). In [[passive optical network|passive optical networks]], Management is provided by the OLT via OMCI, in case of a [[GPON]] connection, and OAM in case of a EPON connection. Authentication and encryption is done via LOID for EPON and PLOAM password, GPON serial number or others for [[GPON]].

== Environmental conditions ==

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* [[CSU/DSU]]

* [[Customer-premises equipment]]

* [[Data circuit-terminating equipment]]

* [[On-premises wiring]]

* [[Data service unit]]

* [[GPON]]

* [[Local exchange carrier]]

* [[Main distribution frame]]

* [[Network termination]]

* [[On-premises wiring]]

* [[Optical modem]]

* [[Optical line termination]]

* [[Point of appearance]]

* [[User–network interface]]