Continuity mistake: When Bryan is interrogating the man using the electrical chair, after he flips the switch the first time, Bryan is seen taking off his tie. However, after Bryan flips the switch the second time, in one of his closeups Bryan is wearing the tie, but in following shots the tie is gone again. (01:05:35)
Visible crew/equipment: When Bryan is talking to Lenore at the party, the boom mic can be seen reflected in Lenore's sunglasses. (00:02:45)
Continuity mistake: When Bryan chases the spotter, all of the cars that had to stop are all positioned at different angles. After the spotter dies and Bryan walks back along the bridge, one of the shots shows all of the cars now parked in a perfectly straight line.
Continuity mistake: When the spotter is organising with the girls to go to the party outside their apartment, behind him you can see a grey Peugeot 806 people carrier with nothing behind it. In the shot as he walks away, a dark coloured car has now appeared behind the Peugeot - not enough time had passed for that to happen.
Continuity mistake: When Bryan goes into the store to buy the karaoke machine, there is a clock visible on the wall behind the merchant. During this scene, the minute hand jumps ahead by 5 minutes between the first shot of the merchant and the second shot 6 seconds later. (00:01:55)
Continuity mistake: When Bryan meets his daughter in the restaurant and gets her a milkshake with three cherries, as the scene cuts from Bryan to his daughter and back, the whipped cream goes from being on top of the milkshake to melted and then back again to being on top.
Continuity mistake: When Kim runs to hug Bryan at her birthday party, her braid in the first shot showing her face is behind her back. In the next shot from behind her, her braid is over her right shoulder. In all subsequent shots, it remains over her shoulder. (00:03:40)
Answer: Actually, what Bryan Mills did was perfectly possible. He strapped a mobile phone to the two way radio, and used the other two way radio to talk. By speaking into his radio, it transmitted it to the other radio, where the mobile speaker could hear and transmit his voice. The French police would have been able to triangulate the source of the mobile phone signal from the particular 'cell' (i.e. area) that the mobile was using - while that would lead them to the phone position, he'd be elsewhere talking on the other half of the radio.
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