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What Is ISDN? The Integrated Services Digital Network Explained

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Want to establish an effective and easy-to-use business phone system? Here is an in-depth post about Integrated Services Digital Network (ISDN), how it works, major benefits for business uses, and viable alternatives.

Integrated Services Digital Network Explained

Integrated services digital network or ISDN is a telephone network system. ISDN uses circuit switches to send and receive voice and data through a digital copper line. This phone system was created to replace old landline technology and make it more digital. By doing so, ISDN provides better speed and transmission quality.

How Does ISDN Work?

When users do not have access to a Digital Subscriber Line (DSL) or cable modem connections, then ISDN is the best solution for high-speed internet. To set up ISDN, you will have to work with your ISP and have a working POTS line and phone number.


When discussing phone-internet services, you will come across a variety of terms such as ISDN, PSTN, POTS, DSL, etc. So, let’s discuss and define some related terms and how they work.

A public switched telephone network is a phone network that uses fixed lines with copper wires to connect users. While the phone network service is almost entirely digital now, the signal transmitted from one user to the next is still analog. Common PSTN features include:

  • Line hunting
  • Voicemail storage
  • Fax line
  • Custom messages
  • Caller ID

ISDN works as an integrated service. In other words, it is used to transmit voice, video, data, and other unified communications between users. By adopting ISDN, users (businesses) do not have to purchase, install, and manage multiple PSTNs. Common ISDN features include:

  • Multiple numbers in a block
  • Extensions and DID numbers assigned to individuals or departments
  • Line hunting

DSL takes ISDN to the next level by digitizing the system. And by doing so, it transmits data quickly and with better quality. But how does it do so? ISDN is a dial-up service that works through one line whereas DSL is always connected and does not need to be dialed to work. This results in DSL sending packets at a speed of up to 100Mbps, while ISDN slows down after 128Kbps.

4 Major Benefits of ISDN

So, why should businesses opt for ISDN and what benefits can they expect from this service? Here are four major advantages of an ISDN connection:

  • ISDN offers better quality and faster data transmission. By doing so, it provides a higher data transfer rate.
  • Allows for multiple data transmissions simultaneously.
  • Users can access multiple digital services through the same copper wire.
  • Users can operate multiple devices (phones, computers, fax machines, credit card readers, etc.) through the same line.

what is isdn

ISDN Alternative: VoIP

While ISDN seems like an effective business communication service, it is not the most cost-effective option out there. A popular alternative to ISDN is voice over IP. A VoIP phone system converts audio signals into digital signals and transmits them from one user to the next through an internet connection.

By doing so, VoIP lets users make and receive calls without the need of a physical telephone line. Additionally, users can operate this service from any location and through any device of their choosing, making business communications more reliable and accessible. Benefits of using a VoIP phone system include:

1. Cost-effectiveness: A landline phone system costs about $50 for a line that can only call local and domestic numbers. VoIP, on the other hand, gives users access to local numbers and international toll free numbers, and more for low, bundled prices.

2. Features: Gain access to a variety of advanced virtual communication tools such as:

    1. International call forwarding
    2. Extensions for different departments
    3. Creative and effective call management tools
    4. Outbound calling with a dynamic caller ID
    5. Call recording
    6. Call analytics

3. Accessibility and Flexibility: Be available and accessible from any location and device. Make remote working possible and accountable by using a reliable phone system.

4. Scalability: Grow and expand your business phone system as and when needed. Installing new VoIP lines does not mean installing a new connection but acts more like getting a new username which can quickly be connected to a device.

Want to Learn More?

Our telecom experts can help you understand the different types of phone communication services and features available. Furthermore, you can identify which services and tools can boost your specific business’ image and customer relations. Call us today or chat with us online to learn more about the options ahead!