The 1756-N2 is an empty slot cover for the ControlLogix series manufactured by Allen-Bradley (Rockwell Automation). This module is typically used to cover empty slots in the ControlLogix case to protect the internal circuitry from dust, dirt, or other impurities. It is a single slot width virtual module that does not contain any electronic circuits, so it is also known as a virtual module or empty slot filled card.

The characteristics of 1756-N2 include:
High protection performance, can adapt to a variety of harsh working environment.
High stability and corrosion resistance, usually made of high-strength materials.
Easy to remove and install, easy to clean and maintain.
Suitable for mounting locations where high levels or numbers of dust particles or small contaminants may stick to the backplane.
Provides an additional layer of protection against gases, vapors and other industrial contaminants.
1756-N2 Hollow tank covers are widely used in various industrial fields, such as machinery, electronics, automobile manufacturing and other industries, for protecting equipment or devices from the external environment. It is also suitable for situations where the interior of the ControlLogix system needs to be protected from contamination.

The 1756-N2 has an operating temperature range of 0°C to 60°C (32°F to 140°F) and a storage temperature range of -25°C to +60°C (-13°F to +140°F). It measures 157mm x 229mm x 133mm, weighs about 2.3kg and is made of aluminum alloy.