The Difference Between ISDN and PSTN – and Why You Should Care

Many new businesses simply assume that a landline is just a landline… until they actually go to sign up for one.

isdn pstn

In a Nutshell

PSTN or Public Switched Telephone Network is the original and still the most common form of telecommunication connectivity and is a much-needed part of many businesses. It supplies a single phone line and telephone number.

ISDN or Integrated Services Digital Network is a digital, fixed line service providing high capacity, directly connected voice and switched data. ISDN transforms your existing phone line into the equivalent of 2-30 digital lines depending on which plan you choose. Each digital line can handle both voice, image, data and video.

Both can be used as business landline, but as can be obviously derived from the above definitions, ISDN performs well and is the most prevalent choice in today’s businesses.

That’s not to say PSTN is out of the equation. Here’s a short comparison over the two.

The Rundown

PSTN is also called POTS (Plain Old Telephone System), and as the name dictates, precedes ISDN connections, supplying a single phone line with a single phone number, which most households are already familiar with.

This service is good for smaller businesses like bakeshops, salons or convenience stores that require only one or two lines. It is also recommended for services where a dedicated line is necessary, such as EFTPOS or fax machines, ADSL connections and even back-to-base alarm systems.

The ISDN or what I like to call “PSTN on steroids.” It provides multiple channels per line, and allows multiple concurrent phone calls. Each of these lines is able to carry both data and voice services. These lines typically deliver better bandwidth than PSTN lines, which makes them well suited for services including video conferencing and data transfers.

This type of phone connection is the ideal choice for medium and large businesses, and is typically linked to office phones through a PBX system.

For many businesses, only 30-40 percent of their phone lines are actively in use at any one time. This means that in an office with 10 staff where everyone uses their own phone, they would require either 10 PSTN lines or as little as 4 ISDN lines. This makes ISDN more cost effective for businesses, especially in larger offices. Using ISDN lets all phones within a business to have a unique phone number, which people from outside the business can dial directly (also called a DID or Direct In Dial number).

The Summary

So, ISDN vs PSTN: which is the best choice for your business? Both systems have their benefits, and the right solution for your business may well be the use of a combination of the two. Whatever the case, it makes sense to research a good ISDN/PSTN service provider online and talk to their client professionals (if available) to assist you with your concerns and help you pick the perfect solution for your business.

As a general rule, the best solution for many medium to large business is to apply ISDN as their major phone lines, plus a few PSTN lines for stand-alone services. Smaller businesses on the other hand can benefit from simply using PSTN lines. However, with the future company growth as consideration, the more lines you require, the more economical ISDN becomes.