I had a chair in my viva. He was responsible for organising the viva and liaising with examiners. In the viva itself he explained the procedure to me at the start, then let the examiners take over. He was allowed to ask me questions, but did not take part in the decision over my PhD result.
And he was the person I liaised with over my corrections. I emailed the corrected version of the PDF to him, and then the signed hard bound versions were delivered to him to sign off and send on to Registry.
But the procedure may vary by university.