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Communicating at high speed

Boy with bike delivering Telegram, 1930s

Speed of transmission : how fast can you send the message?

Originally, sending a telegram was a cumbersome and slow process. You had to send the message using a relatively complex code letter by letter, only to have to reverse the process at the receiving end.

These delays were significantly reduced by teleprinters (in a system known as Telex), which allowed users to type their own messages at a keyboard and send them at the press of a button.

Early telephones had a different kind of delay - calling the operator, giving her the number and waiting while she and possibly other operators involved in the call made the connection entirely manually. This has been speeded up by letting users dial their own calls which are then connected using automatic equipment.

There are sending delays on the Internet as well. It takes time to compose messages, to upload them to the 'server' computer and for them to become available to others. Sometimes the process seems fast - sometimes painfully slow. It all depends on the volume of network traffic - and also what you're used to.

International telephone operators, 1930s

Speed of connection : how fast can a signal travel?

Signal transmission speeds are the fastest thing about telecommunications - but even these are not 'instant'.

Electromagnetic impulses travel at the speed of light - but over distances of hundreds or thousands of miles that means a tiny delay.

A more significant cause of delay is what's being done to the signal to squeeze it down the line. Compression, multiplexing, decoding and decompression - all these steps cause successive minute delays, and there will be more if the signal has to be beamed 40,000 miles out into space, bounced through a satellite and beamed back down to Earth.

The end result of all these delays - a pause of about half a second between speaking on a transatlantic phone call or live television link and your voice reaching the listener - doesn't seem much, but when you're trying to hold a conversation, via space, it can be disruptive and annoying.

BT Broadband CD

Speed of reception : how fast can you pick up a signal?

As well as delays in sending signals there are also delays in receiving them. It takes time for signals to be decoded and transcribed into ordinary language.

With the telegraph, this meant waiting for the signal to come through in Morse - as audible clicks or in series of needle movements - writing all that down, decoding it, writing it out as a plain language message, giving it to a messenger and actually taking it to the person whose name was on the message.

In the Internet age, the delay is much less - but still measurable. With an e-mail, you have to:

  • wait for it to reach your domain name server

  • wait for it to come down the line, through your modem and into your computer

  • wait for it to be stored on your hard drive

  • wait to be told that the mail is there

  • wait to be 'logged on' and able to open it.

Using a high speed connection such as ADSL, the transmission delays are small, but the human and service delays are significant. Usually it takes a few seconds - sometimes it can take hours.

Surfing the net - Internet users

Speed of understanding : how long does it take you to 'get it'?

The longest delay to any signal or message is usually the human factor - which depends on how well different methods of communicating fit into the ways in which we instinctively want to communicate.

The delays caused by technology are usually measured in seconds - sometimes minutes. But the delay caused by human factors can take hours, days or weeks.

Take the example of an e-mail. The time from pressing 'Send' to the e-mail reaching the target domain name server is normally less than 30 seconds. Sometimes it can be as much as 15 minutes if the network is very busy. But the delay before the receiving person actually finds that mail, opens it and reads it can be days.

And you might have to wait forever for a reply ...

fun and games

Can you beat our games? Explode equipment to see what's inside, hear the changing sounds of telecommunications, see how telecommunications designs have changed over time or send an e-postacard.

what's on

The UK's first permanent gallery dedicated to the history of information and communication technologies opens in the new Information Age gallery at London’s Science Museum.

audio history

Take a trip down memory lane with extracts of the interviews which have been recorded as part of the Connected Earth oral history programme.

featured story

100 years of automatic switching!
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