Is this a battery or sound recorder from the 'The Fabelmans' beach scene?

[Daniel D. Teoli Jr.]

 

Is this a battery or sound recorder on the Arri?

Photographs of TV screen

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Daniel D. Teoli Jr. Archival Collection
Daniel D. Teoli Jr. Small Gauge Film Archive
Daniel D. Teoli Jr. Advertising Archive
Daniel D. Teoli Jr. VHS Video Archive
Daniel D. Teoli Jr. Popular Culture Archive
Daniel D. Teoli Jr. Audio Archive
Daniel D. Teoli Jr. Social Documentary Photography

 

[Brian Drysdale]

It's a battery, the cable is plugged into the 2 pin power socket at the back of the camera.