Mark Durenberger, former engineer at WCCO (among many other stations), has donated an old console that he used at WCCO.
Known as "Studio 5," this audio mixer was designed and built by CBS, and through its controls passed all of WCCO Radio's
programming for nearly 4 decades. This panel was the heart of WCCO's Master Control until the late 1970's.
Though this might seem a rather simple assembly for a full-service radio station, it was actually a "Master Mixer".
Each knob could control the output of several other pre-mixed program sources, collectively including several dozen
microphones, turntables, tape and disc recorders, the CBS Radio Network and dozens of "remote" telephone circuits
that enabled WCCO to broadcast from throughout the country.
During typical "in-studio" operation, the bottom row of controls adjusted the main talent microphones and the top
row included faders for "Remotes", the CBS radio network and the custom telephone system, and a "Transcription ('ET') Bus"
(on which appeared all the tape recorders in the building as well as turntables in the control room).
The Studio 5 audio mixer 
Here it is in place with the other equipment. The "Pre-Selector" and the meters for the 4 output channels can be seen under
the clock. In the rack to the right of the clock was the key bank that selected from among dozens of incoming telephone
lines used for the "remote" broadcasts.