Integrated Services Digital Network facts for kids

Integrated Services Digital Network, often called ISDN, is an old but important international standard for communication networks. It was mainly used with telephone lines. Before ISDN, phone lines were mostly for making voice calls. These calls used an analogue signal, which meant a direct connection was made between two phones for the call.

ISDN changed this by making the signal digital. This meant telephone lines could carry more than just voice calls. They could also send different types of data. Before ISDN, services like telex (for sending text messages) or teleprinters (like early typewriters that could send messages) used their own separate networks. There were special connection points, called gateways, to link these different networks.

With ISDN, this changed. Instead of many separate networks, there was one main network that could handle different services. Some services were for voice, like making phone calls, while others were for data, such as sending telefaxes.

How ISDN Works

ISDN uses special channels to send information. It has:

• Data channels: These channels carry the actual information, like your voice during a call or the data for a fax.
• Signaling channel: This channel is like a control channel. It tells the network how to set up and manage the calls or data transfers.

Basic ISDN Setup

The most common ISDN setup for homes and small offices had two data channels. These two channels could work completely on their own. For example, you could be talking on the phone using one channel while sending a fax on the other.

If you wanted a really clear phone call, you could combine both data channels into one. This would double the amount of information for the voice call, making the sound quality much better.

ISDN for Businesses

Larger companies could use a version of ISDN with many more data channels, sometimes up to 30! They would still use just one signaling channel to control all these data channels. This allowed businesses to handle many calls and data transfers at the same time.

Images for kids

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  An ISDN telephone

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  An old ISDN box on a wall

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  A German stamp showing ISDN

See also

In Spanish: Red digital de servicios integrados para niños