Time travel or something else?

What is this woman doing if not using a mobile phone in 1928. This footage is from a backstage film for the launch of the Charlie Chaplin film 'The Circus' .

Of course there is a vital point to be made here; if the woman is using a mobile telephone in 1928 could someone explain how, as the transmitter/receiver cell masts she could use wouldn't have existed for another 60 years.

So a cell phone seems somewhat unlikely but maybe a more futuristsic piece of communications technology? Is this perhaps the first glimpse of the 12th Doctor?