In an enterprise network, a patch panel serves as a sort of static switchboard, using cables to interconnect network computers within a LAN and to outside lines including the internet or other wide area networks (WANs). Patch panels can also be used to interconnect and manage fiber optic cables..
Patch Panel is a device that has a number of same or similar kinds of jacks; the purpose of the jacks are connecting and routing circuits to interconnect monitor and test the circuits so that it can be ensured that the circuits are working in flexible and user-friendly manner.

Racks organize IT equipment, such as servers and network switches, into standardized assemblies that make efficient use of space and other resources. Depending on the options you choose, they can also improve power protection, cooling, cable management, device management, physical security, mobility, ease of installation and protection from harsh environmental conditions.
Choosing the right racks and configuring them to match your needs will ensure that your IT equipment operates reliably and efficiently, saving your organization from costly downtime and other needless expenses.

Private Automatic Branch exchange (PABX) is an in-house telephone switching system which makes connections among the internal telephones of a private organization (or an enterprise) and also connects them to the public telecom network via various interfaces. ... Initially, Private branch exchanges used analog technology.