In movies and tv, why does a phone go to dial tone after someone hangs up?

January 16, 2005 8:20 PM

In movies and on TV, why does a phone go to dial tone after someone hangs up? Is there a phone system somewhere that really does that?
posted by stopgap to technology (22 comments total)

Not that I've heard of, but it is covered on the Movie Cliche List. It must be one of those illogical, easy-to-understand things that keep the action of the movie going.
posted by Arch Stanton at 8:22 PM on January 16, 2005

It's to make it clear to the audience that the connection is closed. The difference between the silence you hear when no one is saying anything, and the silence you hear just after the other person has hung up, is too subtle for most directors/sound engineers to bother trying to get across. Besides, the sudden dial tone is more dramatic.
posted by bingo at 8:24 PM on January 16, 2005

Yeah, if you missed the click while trying to spit ice back into your drink, you'd think it was just awkward silence.

Tarkovsky would have the click, followed by silence in real time till it started beeping.
posted by Jack Karaoke at 8:32 PM on January 16, 2005

I thought that might be the answer, but that's pretty lame. I'm going to make a list of every time I notice this happening so I can write complaint letters.
posted by stopgap at 8:32 PM on January 16, 2005

Back in the old days, when I was a kid, a phone did go to dial tone after someone hung up (and we liked it that way!) Changed about 30 years ago IIRC.

Might just be a hold over, or what bingo said.
posted by page404 at 9:08 PM on January 16, 2005

On British telephones, if the other person hangs up, you get the click, but then a second later you do get a tone. It's a single tone, rather than a chord like the dialtone, but similar enough.
posted by wackybrit at 10:16 PM on January 16, 2005

Here's a telecom geek's rant. Additionally, they use the dial tone convention for cell phones, which never have a dial tone. This was in one of the Spiderman films, for instance.

The dial tone did return when you were serviced by older mechanical switching equipment; with the move to digital this changed, and in particular standard behavior today incorporates a signal known as CPC (calling party control), which was created to alert devices such as answering machines that a call was completed.

My mother used to take the phone off the hook for naps; one day, she couldn't do that any more, as the very loud off-hook fast-busy tone was introduced locally. Not exactly the same thing, but you see how numerous changes arrived around that time.
posted by dhartung at 10:37 PM on January 16, 2005

Not only do movie cellphones get dial-tones after you hang up, they also get dial tones when dialing (and you can hear the touch-tones too)! Most cell phones don't even produce audible DTMF tones when dialing, and there is no dialtone because there is no connection to the phone system while dialing is in progress.
posted by kindall at 10:46 PM on January 16, 2005

> On British telephones, if the other person hangs up, you get the click, but then a second later you do get a tone. It's a single tone, rather than a chord like the dialtone, but similar enough.

Just to be pedantic, the dialtone is not a chord (which requires the presence of at least three different tones, but is an interval consisting of just two tones (350Hz+440/450Hz)...
posted by benzo8 at 11:40 PM on January 16, 2005

And in similar vein, why does the person who's been hung up on often shout "Hello? Hello?" and whack the hang-up lever a few times. Surely, if the connection was NOT dead, whacking that lever would be a sure way to make sure it WAS dead.
posted by TiredStarling at 7:41 AM on January 17, 2005

My Samsung phones, at least, have always produced DTMF tones when dialing manually. Not when dialling from the internal phone book, of course.

This has been one of my all-time movie-audio pet peeves (up there with the "cocking gun" sound effect). It really bugged me in Spider-Man when the cell phone gave a dialtone -- then I later realized that one of my favorite movies of all time, The Big Lebowski, also has that gaffe!
posted by neckro23 at 7:45 AM on January 17, 2005

"CELL PHONES DON'T HAVE DIAL TONES! PERIOD! EVER!" -- the linked rant

"Most cell phones don't even produce audible DTMF tones when dialing..."

That's odd. Every cell phone handset I've ever owned (and I've been through 8 or 10 of them over the years) simulates a dial tone and emits DTMF if you take it "off hook" (which, yes, I'm aware does not actually take the line off hook) before you dial. Are there models that don't do this? Or am I the last person in the world to dial off hook?

Not that this changes the fundamental problem: Like everything except the most dubious PBX, cell phones don't emit dialtone on disconnection.

There are PBXes that emit a bogus dialtone on disconnect, and certain ancient and insecure types which actually provide a real dial tone from the line pool when the PBX user hangs up. Years ago, 555-1212 (the predecessor to 411) used to give a non-fake dialtone after the information operator disconnected, here in Pac Bell territory, allowing all manner of free calls to be made from payphones.
posted by majick at 7:50 AM on January 17, 2005

And in similar vein, why does the person who's been hung up on often shout "Hello? Hello?" and whack the hang-up lever a few times. Surely, if the connection was NOT dead, whacking that lever would be a sure way to make sure it WAS dead.

Actually, on rotary phones (and maybe on some early touch-tone phones), that 'hang-up' lever, if pressed quickly and lightly, would send a signal that was equivalent to the dialing the number one (or however many times you pressed it). It was actually possible to dial that way if you were careful (why would this be needed? well, say you were a child, and some silly adult had applied a lock to the rotary dial...).

Anyway, back in those days, if one party accidentally pressed the 'hang-up' lever, and then immediately released it, the connection was not necessarily closed. Sometimes, pressing the lever again would have the effect of 'bringing the connection back,' even though it was still there. This became an issue again when call-waiting was introduced...you might think you've hung up on someone, but actually one of you is in 'on the other line' without actually talking to anybody, and 'hanging up' again, would 'restore' the connection.

Sigh...how very complicated, now that I think about it...
posted by bingo at 8:03 AM on January 17, 2005

Actually, the trick of clicking the lever repeatedly to dial still works on any phone system that supports pulse dialing. I've done it myself, out of boredom, and if you need a less credible source it's also done in the movie Hackers.
posted by squidlarkin at 8:32 AM on January 17, 2005

Every cell phone handset I've ever owned (and I've been through 8 or 10 of them over the years) simulates a dial tone and emits DTMF if you take it "off hook" (which, yes, I'm aware does not actually take the line off hook) before you dial.

Uhhhhrrrrr? There's no way to take a cell phone "off hook." You enter the number, then hit SEND. Hitting SEND before you've entered a number doesn't do anything on any cell phone I've ever owned. Well, on my Ericsson it produces a list of people I've recently called or who have recently called me, but it's the YES button not SEND. The idea that there are not one, not two, but eight models that behave in the utterly bizarre manner you describe is mind-boggling.
posted by kindall at 9:12 AM on January 17, 2005

Ok, since there have been so many questions and answers in this tread...on a land line, why is it sometimes impossible to hang up on someone who doesn't hang up their end? I've had calls from annoying people where I hang up the phone and when I pick it up again, they're still there!!! Even when I leave the phone hung up for a minute, it doesn't work...it's such a helpless feeling.
posted by spaghetti at 9:46 AM on January 17, 2005

spaghetti, I think that was alot more common in the past(10 years atleast ago).
I remember you could call someone with a pay phone, then use a rubber band to stop the handset from depressing the hangup lever, and then the person you called would be connected to the payphone for a really long time.
posted by Iax at 11:33 AM on January 17, 2005

Ok, since there have been so many questions and answers in this tread...on a land line, why is it sometimes impossible to hang up on someone who doesn't hang up their end? I've had calls from annoying people where I hang up the phone and when I pick it up again, they're still there!!!

It's called loop disconnect threshold, or disconnect supervision. This became a problem for some when call waiting was introduced. What's happening is that there hasn't been a long enough "wink" on the line to tell the CO to drop the circuit. A wink is a very quick reversal of the -48V battery feed on the line. If it doesn't last long enough, the line remains hung up until another timer overrides it and kills the line. Fixing it involves minor tuning at the CO level, and it's damn near impossible to get them to do it.
posted by TeamBilly at 12:32 PM on January 17, 2005

My cellphone produces faux-DTMF tones as I'm dialing, presumably for audible feedback for the numbers I'm punching in. Not that these tones actually get transmitted to the phone system - and I can turn them off if I'm so inclined - but you can certainly hear them.
posted by youhas at 5:38 PM on January 17, 2005

Just to be pedantic, the dialtone is not a chord (which requires the presence of at least three different tones, but is an interval consisting of just two tones (350Hz+440/450Hz)...

I'm glad you pulled me up on this. As I made my post I got into an internal argument with myself over this. I knew chord was wrong, but I couldn't remember what the right term was.. duet?, diad?, duotone?.. but then realized I was wasting my time so went with chord, assuming everyone would know what it meant.

The thing is, I still can't find the word I wanted. Interval is perfectly fine, of course, but I was sure there was another word for two notes.
posted by wackybrit at 6:51 PM on January 17, 2005

Testing. Ignore please: &þ ⇒ þ and &ʒ ⇒ ʒ
posted by stopgap at 3:29 PM on January 19, 2005

þ ⇒ þ and ʒ ⇒ ʒ
posted by stopgap at 3:30 PM on January 19, 2005