Integrated Services Digital Network


Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous transmission of voice, video, data, and other network services over traditional copper telephone lines. Developed in the 1980s, ISDN aimed to replace the slower and less reliable analog phone systems. Despite advancements in digital technology, it has largely been superseded by broadband internet technologies like DSL and fiber-optic connections.


The phonetic spelling of “Integrated Services Digital Network” using the International Phonetic Alphabet (IPA) would be: ˈɪntɪˌɡreɪtɪd ˈsɜrvɪsɪz ˈdɪdʒɪtl ˈnɛtˌwɜrkPronunciation is divided into syllables as follows:In-te-grat-ed Ser-vices Dig-i-tal Net-work

Key Takeaways

  1. Integrated Services Digital Network (ISDN) is a set of communication standards designed for simultaneous digital transmission of voice, video, and data over telephone lines, providing enhanced quality and speed compared to traditional analog systems.
  2. ISDN comprises two main types of channels: Bearer (B) channels, which carry the actual data, and Delta (D) channels, which handle control signals for call setup and management. These channels are combined into different configurations, such as Basic Rate Interface (BRI) and Primary Rate Interface (PRI) services, to cater to varying user requirements.
  3. Though ISDN was once considered a revolutionary innovation in the telecommunication sector, it has gradually become outdated due to the widespread adoption of more advanced and flexible technologies, such as broadband internet and Voice over IP (VoIP) services.


Integrated Services Digital Network (ISDN) is important because it revolutionized telecommunication services by enabling a single communication line to simultaneously transmit voice, video, and data over digital networks.

Introduced in the 1980s, ISDN offered substantial improvements to traditional analog networks, including higher data transmission rates, better reliability, and reduced background noise.

This innovation ultimately laid the foundation for further advancements in digital networking technologies, paving the way for modern broadband internet connections, digital video transmissions, and advancements in voice over IP telephony.

In essence, ISDN serves as a milestone that marks the evolution of telecommunications from analog to digital systems, which has been crucial in driving today’s interconnected information age.


Integrated Services Digital Network (ISDN) emerged as a revolutionary telecommunications technology that aimed at providing enhanced and reliable communication services compared to the traditional analog telephone systems. The purpose of ISDN was to deliver high-speed digital connectivity by transmitting voice, data, and video over copper wires, thereby streamlining the whole communication process. This technology came into existence during the 1980s and 1990s, when the need to improve the existing telecommunication infrastructure became necessary with the growing reliance on digital communication for both personal and professional purposes.

ISDN made it possible for various services and devices like telephones, fax machines, and computers to be interconnected using a singular, stable, and digital network, resulting in better-quality calls and faster data transmission rates. ISDN served as a stepping stone for advanced communication technologies. It facilitated simultaneous data transmission, allowing multiple devices to send and receive information efficiently over the same network.

This technology proved to be pivotal in areas such as internet access, teleconferencing, and remote workstation operations, where seamless exchange of voice, images, and data was critical. Moreover, ISDN allowed businesses to establish elaborate and efficient communication systems quickly, without the need for costly fiber-optic installations. Although newer technologies like broadband and VoIP have now surpassed ISDN, its contribution to the evolution of digital communication systems remains invaluable, as it laid the foundation for modern telecommunications infrastructure across the globe.

Examples of Integrated Services Digital Network

Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuit-switched telephone network. Here are three examples that showcase how ISDN has been utilized in the real world:

Video Conferencing: Before the emergence of broadband internet, many businesses relied on ISDN for video conferencing. Since ISDN offers a reliable and high-quality connection, it was great for conducting real-time video meetings. Companies with branch offices in different locations were able to save travel time and costs by connecting via video conferences using ISDN lines.

Broadcast Media: In the broadcasting world, ISDN found its use through providing on-demand, high-quality audio transmission to radio stations. For instance, radio journalists who needed to conduct live interviews remotely, or provide breaking news reports from the field could use ISDN as a means to transmit their voice data in high quality and with low latency. This technology helped to ensure clear and reliable audio feeds for radio programming.

Remote Access to Databases and Resources: ISDN enabled professionals to access centralized databases and resources at their workplaces while working remotely. In the pre-broadband era, ISDN offered a faster and more reliable connection than traditional dial-up connections. This improved access to information and allowed people to work efficiently from remote locations. Universities, research institutions, as well as some businesses made use of ISDN connections for this purpose.

Integrated Services Digital Network (ISDN) FAQ

What is Integrated Services Digital Network (ISDN)?

Integrated Services Digital Network (ISDN) is a set of communication standards that enable simultaneous digital transmission of voice, video, and data over traditional copper-based telephone lines. It was developed to replace traditional analog communication systems with a more reliable and faster method for transmitting data.

What are the main components of ISDN?

ISDN consists of three main components: Basic Rate Interface (BRI), Primary Rate Interface (PRI), and Broadband ISDN (B-ISDN). BRI and PRI both use digital channels for transmission, while B-ISDN is designed for high-speed data transfer using fiber optic technology.

What is the difference between BRI and PRI?

BRI, or Basic Rate Interface, is typically used for residential and small business customers. It offers two 64 Kbps B-channels for voice and data transmission, and one 16 Kbps D-channel for signaling and control. PRI, or Primary Rate Interface, is designed for larger organizations and provides more bandwidth with 23 B-channels (30 in Europe) and one 64 Kbps D-channel. This allows multiple users to simultaneously access the ISDN network with more capacity.

What are the benefits of using ISDN?

There are several benefits of using ISDN, some of which include faster data transmission, improved voice quality, and the ability to transmit multiple types of data simultaneously. Additionally, ISDN can provide a more stable and reliable connection compared to traditional analog lines.

Is ISDN still in use today?

While ISDN has largely been replaced by more advanced communication technologies such as DSL, VoIP, and broadband, it is still in use in some remote areas and for certain applications where its reliability and established infrastructure provide advantage over newer technologies.

What is the relation between ISDN and DSL?

ISDN and DSL (Digital Subscriber Line) are both methods of providing digital data transmission over traditional telephone lines. However, DSL is considered a successor to ISDN, offering higher bandwidth, faster data transfer rates, and greater flexibility for the end users. DSL technology operates by transmitting data over a larger frequency range, allowing for simultaneous voice and data transmission without interference.

Related Technology Terms

  • Basic Rate Interface (BRI)
  • Primary Rate Interface (PRI)
  • Signaling System 7 (SS7)
  • Non-Facility Associated Signaling (NFAS)
  • Digital Subscriber Line (DSL)

Sources for More Information

  • Cisco –
  • Techopedia –
  • Computerworld ––integrated-services-digital-network–isdn-.html
  • The Free Dictionary –

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