Multiple audio sources wired into an intercom can create a “ground loop.” The Problem can be solved by inserting a ground loop isolator, like this one.

Multiple audio sources wired into an intercom can create a “ground loop.” The Problem can be solved by inserting a ground loop isolator, like this one.

Multiple audio sources wired into an intercom can create a “ground loop.” The Problem can be solved by inserting a ground loop isolator, like this one. Photo by Wayne Roth.