'Cellular' technical question

Saw the movie this weekend and it was pretty good for a ‘B’ movie, but further on that is for CS. My question is this: The Hero and the Victim are linked together by a tenuous cell phone connection. At one point their conversation is broken into by another call and all four parties (both halves of two different calls) can talk to and hear each other. The original connection we care about is lost just as the Hero spots the Jerk whose call they were sharing, so he steals the guy’s car (and phone) to continue the chase (Like I said it’s a B-movie).

Is this scenario even possible, or is it another case of Hollywood technology run amok? In (presumably) the hand-off from one cell to another, can the network get confused over which call goes to which phone?


I believe it would have been possible in the days of analogue mobile phones. The best advertising digital ones ever got was when Prince Charles’ calls got tapped into.

Not really. Analog phones were easy to listen in on using radio scanners because the signal was unencrypted, it’s true. But, it was still impossible for a phone to receive calls meant for a different phone (barring so-called “cloning”), because the ESN (electronic serial number) embedded in the signal needed to match the phone it was intended for. Otherwise, it would have been impossible for multiple phones to share a single frequency.

I think conference calling is possible on some/all networks in the UK (on some billing packages, I’m not sure though, whether the connection is maintained after the originally-connected pair have terminated.

What does “broken into” mean? 3-way calling is available on cells (my company offers it as a standard feature) but breaking into a call in progress is unheard of. As Q.E.D. mentioned, cells all have unique ESNs that cell towers use to ID each cell.

“Cloning” is the use of someone elses ESN to make calls and trick the system into thinking person “A” made a call that person “B” is actually making, thus making a free call (and charging poor person “A”). Cloning is no longer possible with the advent of modern digital cell phones (and network authentication).

I wanted to amend my post (damn no editing!). I shouldn’t say it’s unheard of to intercept a cell call but digital cells are very very difficult to intercept (analog calls can be intercepted but analog towers are quite rare around here).

Digital cells use fequency hopping and encryption (ours do anyways) so unless you’re bugging the cell tower, it’s virtually impossible to intercept a digital cell phone call.

Well, as presented in the movie, Hero is driving and talking to Victim, trying to figure where she’s being held. Then her voice starts breaking up and fragments of another conversation start intruding. Confusion reigns for some seconds – “Hello?” "Who is this? “Get off my line!” – and somewhere in this, the Jerk’s other half hangs up, leaving Hero, Victim, and Jerk talking to each other. Victim’s voice breaks up more and more, then is no longer heard, just Jerk’s. Hero stares in horror at his phone screen, which reads ‘Incoming Call Lost’ but he can still hear Jerk. POV changes to Jerk stopped at a light, who can still hear Victim and is yelling at her. Just then, Hero drives past, hears Jerk through the window and on his phone, realizes what’s going on, and stops, waving a gun.

Seemed pretty unlikely, technologically speaking but it gave Hero a chance to drive around in a Porsche for a while.


More like impossible, based on your description. This sort of thing does happen with AM radio as you drive along. The station you’re listening to will get weaker and more staticky, and you may hear another station on top of it, and then the new station gets stronger until you can no longer hear the old one at all. This can’t happen with cell phones, even the older analog ones, because of the ESN thing I mentioned earlier. Even if the signal were weak and noisy enough to cause the receiving circuitry to mistakenly flip a bit here or there creating an inintended spurious ESN match, it’s a practical impossibility for this to happen consistently enough to erroneously receive enough data packets to assemble an intelligible call.

Oh, Hero’s phone was digital, all right. Besides the fancy LCD screen, it had the built in camera. It became a Big Plot Point by the end of the movie. And, yeah, the breakup and overlay sounded a lot like adjacent AM stations. Living way out west, it’s a familiar phenomenon.