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  • Brace yourselves, we're about to get into some serious detail about telephone systems.

  • I'm at the Museum of Communications in Seattle, to answer a question:

  • in old Hollywood films, when someone is on a phone call and they got hung up on,

  • why did they hear a dial tone?

  • [dial tone]

  • "Well, you can stick your well-laid plan up your well-laid ass." [dial tone]

  • Supervision is the word that describes how a telephone switch

  • knows whether the calling and called parties are on hook or off hook.

  • When you end a call and hang up,

  • the equipment receives that on-hook signal,

  • and anything that was in service at that time

  • disconnects and goes back to its normal state.

  • So you end up with dead air.

  • Now, the reason that a sound director would use a dial tone

  • instead of just nothing is kind of obvious, right?

  • It's to make it clear that the other side has hung up.

  • That's certainly what lots of people argue online.

  • Except they could just do that by using one short sound effect.

  • And sometimes, they do.

  • "Don't ever call me again."

  • [rattling click]

  • "Wow!

  • I...

  • I guess you're home."

  • "Good luck."

  • [rattling click]

  • It turns out there's another reason.

  • Back in the days of celluloid film,

  • southern California was one of the few places in America

  • with independent telephone companies,

  • not part of the giant Bell monopoly that handled the rest of the country.

  • Well, behind us is a step-by-step system

  • and it's a relative of the telephone systems

  • that were used in most of southern California.

  • The Bell system didn't have as much of a monopoly there.

  • As I dial a number, various elements of the step connect me

  • through the system from start to finish.

  • And that's where it got the name step-by-step.

  • As I finish dialling, the call will connect...

  • [ringing]

  • ...and it can be answered.

  • Now, in the step system, it doesn't have what's called 'far-end supervision'.

  • And that means that the called party can hang up and pick up again

  • as many times as they want, and the call won't disconnect.

  • But if the calling party hangs up...

  • [dial tone]

  • ...the called party will get hit with dial tone right away

  • because the system doesn't know whether I've been hung up on

  • or whether I've just picked up the phone.

  • So in Hollywood, where all of the movies were being written and filmed,

  • their experience on the telephone was actually different

  • from most of the rest of America, and the world.

  • Which, let's be honest, is kind of like so many other things in Hollywood.

  • The bottom line is:

  • the folks making the movies really did get a dial tone when they were hung up on,

  • at least sometimes, so they put that in their films.

  • Or they picked whichever option worked best for the scene.

  • If it's still happening when a character uses a cell phone, though?

  • That's just lazy.

  • Thank you to all the team at Seattle's wonderful Museum of Communications!

  • You can check out their YouTube channel over here

  • or pull down the description for a link to the Museum and to see their opening hours

  • and a list of all the incredible equipment they've got here.

Brace yourselves, we're about to get into some serious detail about telephone systems.


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老電影裡,為什麼有人掛斷電話後會出現撥號音? (In Old Movies, Why The Dial Tone After Someone Hangs Up?)

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    林宜悉 發佈於 2021 年 01 月 14 日