What is this device?

[gadje]

https://youtu.be/OU6jHvVqJxY?t=292

There is a black 45 degree prism behind him.

[Ombligo]

It is a teleprompter.

A script is shined up from below it and it reflects on the glass plate so that a person looking at the camera can read. The camera shoots straight through it without any distortion. It replaced cue cards because the readers eyes can remain fixed directly at the camera rather than flitting between the camera and the cue-card.

[gadje]

Thank You!