Network interface device: Difference between revisions

Revision as of 09:53, 10 December 2021

Revision as of 15:08, 10 December 2021

Line 24:

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

== Smartjack ==

Line 33 ⟶ 32:

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 smartjaksmartjack 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.

Line 40 ⟶ 39:

Smartjacks typically derive their operating power from the telephone line, rather than relying on premises electrical power, although this is not a universal rule.

== Optical network terminals ==