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A professor gave a two-hour
lecture but didn't know he was on
. The
on his iPad was switched off. This meant
of the students in his class could hear
. His university switched his classes online to reduce the
of COVID-19. His lecture started
but then the screen on his iPad froze. The video came back but the mic was
. The professor did not notice. It might be
he used an iPad and
a computer.