How Does Isdn Work?

By Michiel Van Kets

ISDN is a digital telephone line that is primarily used for Business telephones.

ISDN (Integrated Services Digital Network) is a system of digital phone connections which is compatible with the existing (analog) telephone system. ISDN customers can use their phones to make conventional (analog, dialup) voice connections. In addition, ISDN customers can make high-speed digital data connections with other ISDN-capable telephone customers.

ISDN allows data to be transmitted and received around the world using end-to-end digital connectivity. With ISDN, voice and data are carried by 64Kbps bearer channels (B channels). Multiple B channels can cooperate to provide higher data rates. Common ISDN installations can easily be configured to use two (2) B channels, providing a true data rate of 128Kbps. In all ISDN installations, a data channel (D channel) handles control signalling at 16 kbps or 64 kbps, depending on the service type.

Typical applications include call centres and offices requiring large numbers of multiple lines or extensions. ISDN provides Business Phone users with digital access to switched voice and data over a single integrated network connection.


ISDN 10/20/30 is a premium business grade service for all local, national, mobile, international and special service calls.

ISDN 10/20/30 provides : significant cost savings as multiple services can be delivered down a single copper pair of wires faster. Call dialling and disconnection is faster allowing for increased efficiency and the indial feature allows you to direct dial extensions rather than go via a switchboard or receptionist.

ISDN comes in two basic configurations. ISDN 2 Basic Rate (BRI) or ISDN 10/20/30 Primary rate (PRI)

ISDN 2 which is suitable for Business that require 2 or multiples of 2 phone lines. e.g. 2, 4, 6 or 8 phone lines.

ISDN 10 20 30 is known as a Primary Rate PRA Digital ISDN service whereas ISDN 2 is known as a Basic Rate Service. A ISDN Business Phone Line is a digital service that provides enhanced functionality via Digital Transmission and can re place conventional analogue telephone lines. It is available in configurations of 2, 10, 20 or 30 channels. ISDN 10/20/30 Business Phones can provide up to 30 x 64kbps channels making it suitable for small or large applications.

A Direct In-Dial is a range of 100 numbers allocated to your ISDN service. It is sometimes referred to as 100 Number range. Direct In-Dial ranges are always in blocks of 100 and are only available on ISDN2 and ISDN 10/20/30 services. In-dial ranges always start with 00 as the last two digits and end with 99 as the last two digits of the range. Multiple In-Dial Ranges can be supplied on a single ISDN service on Telaustralia Telstra and Optus services.

Even though you may only have 2/4/6 lines you can have 100 numbers and this allows you to allocate a direct dial number for any individual or department with your company. This allows you to efficiently manage your calls by directly internal and direct calls to the desired locations while retaining the ability to direct certain advertised numbers via a receptionist or call centre.

With a Direct In-Dial range you are also have access to Extension Level billing which allows you to bill calls out via each extension of the 100 number range. Typical application for this would be serviced offices where the calls need to be metered or call costs from a particular extension billed back to a customer or department.

Direct In-Dial is available on : ISDN 2 Phone Lines and ISDN 10/2030 and ISDN Multi Line.

About the Author: Michiel Van Kets writes articles for TelAustralia, an Australian provider offering a full suite of

ISDN 2 Phone Lines

. With free installation, you can now enjoy the reliability of Telstra Network for

ISDN 10/20/30 Phone lines

and ISDN 1023030 Telephone lines.


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