Meaning – The term loop adapter, refers to a feature of the IBM 4300 Processor family that allows the attachment of a variety of SNA and non-SNA devices. To VTAM, these devices appear as channel-attached type 2 physical units (PUs).
Loopback (also written loop-back) is the routing of electronic signals or digitaldata streams back to their source without intentional processing or modification. It is primarily a means of testing the communications infrastructure.
A loopback adapter is required if you are installing on a non-networked computer to connect the computer to a network after the installation.
Example of usage – “Where a system (such as a modem) involves round-trip analog-to-digital processing, a distinction is made between analog loopback, where the analog signal is looped back directly, and digital loopback, where the signal is processed in the digital domain before being re-converted to an analog signal and returned to the source.”