“I have a question. Do we really need to add PSTN Conferencing on?”

This question came from a prospective customer, during our planning stage for a Skype for Business/Office 365 rollout.

I was not present at the meeting; my co-worker told me about it later. When I heard the question, it made me think a moment. DID you really need PSTN Conferencing?

Let’s explore the idea, shall we? Who knows, it might figure into your own Skype for Business planning!

What PSTN Conferencing Does

First, a little about the PSTN Conferencing feature.

The Skype Meeting tool allows people to join a meeting space using their computers, or an app on their phones. Then they can share voice, video, a desktop, a whiteboard, etc.

But what if you don’t have an app or computer available? Or you’re on the road with no Wi-Fi? How do you join the meeting?

PSTN Conferencing lets you dial into the meeting with your phone. Just call a specific number and you’re in the meeting. The PSTN Conferencing feature enables you to create the dial-in number (or numbers) within Skype for Business.

How PSTN Conferencing Works in Skype for Business Online

In Office 365’s Skype for Business Online, PSTN Conferencing is an add-on. You have to buy it from within Office 365 Admin on a per-user licensing basis.

Set up dial-in or PSTN conferencing for Skype for Business – Office Support

The add-on costs $4/month per user (unless you’re on Office 365 E5). That’s $48/year per user. If you have 100 users who need PSTN Conferencing, you’re looking at almost $5,000 per year, every year.

Now, not every user needs a PSTN Conferencing license. Only those who plan to schedule Skype Meetings or lead them will need one. Regular attendees don’t.

How PSTN Conferencing Works in Skype for Business Server

In Skype for Business Server, the feature is actually called “Dial-In Conferencing.” You need two things to make it work: a Mediation Server and a PSTN Gateway.

Enterprise Voice Calls
Hello? Is the dial plan on?

The Mediation Server is required for Enterprise Voice, and a PSTN Gateway translates signals between Enterprise Voice and a PSTN or PBX. If you want to call out, you’d need both of these anyway!

You also need to configure a dial plan, access number, and conferencing region. Once Skype for Business is deployed, that’s relatively simple to add in. The full requirements are listed in TechNet: Plan for dial-in conferencing in Skype for Business Server 2015 – TechNet.

(You can also use a third-party solution for PSTN Conferencing, if your Skype4B Server deployment isn’t set up like this. Communiqué makes one, for instance.)

We’ve had Dial-In Conferencing installed on our internal Skype for Business Server (and Lync Server before that) since deployment. I’d never thought about it as anything other than “just a part of the system.”

But as I think about it, I realize I’ve never actually used the dial-in number. Even on my phone, I’d use the app. Does anyone else?

I asked around the office. Only one person had ever used the dial-in number, twice while driving/stuck in traffic. Aside from that, we didn’t actually need Dial-In Conferencing!

How Many People Use PSTN Conferencing to Dial In?

As mentioned above, PSTN Conferencing’s core functionality is to provide a number for calling into conferences/Skype Meetings.

Here’s the question: Who will you have calling into your conferences?

Think about the purposes behind your conferences.

  1. Team status updates?
  2. Project discussions?
  3. Sales/New customer meetings?
  4. Management roundtables?

I could go on, but one thing’s clear – many purposes exist for having a conference. But do all of them require external dial-in access? No.

In fact, only #3 above would benefit from dial-in access. And that’s only if…

  1. You’re meeting with a non-local customer who doesn’t have Internet access.
  2. A regular phone call won’t suffice, and again, no Internet access available.
  3. Nobody has Skype for Business, or Skype, installed on their computers/phones.
  4. The Skype for Business Web App isn’t working.

PSTN Conferencing May Age Out of Use, in Time

Of course you’ll want to have phone numbers where customers can reach you. That’s what Enterprise Voice (and Cloud PBX) are for.

But a conferencing dial-in number suddenly seems like less of a priority. Besides, if an external user or customer did need to join your meeting, you still have the Skype for Business Web App.

I guess it comes down to Phone vs. App. What do you prefer – calling phone numbers, or using an app? It’s only my observation, but more and more people are leaning toward App.

Which makes things like PSTN Conferencing an add-on of the past.

When deploying Skype for Business, examine your user base. Consider what kinds of Skype Meetings you’ll hold, and who will attend. It may be that you can rely on apps—and not need the time/cost of installing PSTN Conferencing.

Do you still use PSTN Conferencing? What are your thoughts? Please comment or email.

Do You Really Need PSTN Conferencing?

9 thoughts on “Do You Really Need PSTN Conferencing?

  • March 7, 2017 at 5:42 am

    When you have poor internet connections and need clear voice for your meeting PSTN is clearly the answer. You sometimes do not wish to compromise on sound if it is an important conf call.

    • March 8, 2017 at 8:16 am

      Thanks for the comment. You’ve illustrated an instance where someone would indeed need PSTN Conferencing…and/or a faster Internet connection. I realize that’s not always easy to get, but I hold out hope it will become easier with time.

      Interesting website, by the way!

  • March 12, 2017 at 1:37 pm

    Hi, PSTN Dial-In Conferencing is a high required feature in every of our Lync/SfB deployment (Italy), even in those one with limited Enterprise Voice feature. We’ve customers that setup PSTN access ONLY to get Dial-In Conferencing, not only in customer’s country, but all around the world with on DID number for every country where they are present.
    For many customers voice is foundamental, and PSTN Dial-In is here to guarantee voice.
    Best Regards

    • March 13, 2017 at 1:14 pm


      Great comment. In fact, I’m curious as to your SfB deployment topology. Maybe I could talk you into a post exchange sometime…?


  • October 20, 2017 at 8:18 am

    One of the advantages of this feature is that you can call out to invite attendees over PSTN.

    They get a message saying “YOU ARE NOW JOINING THE MEETING”.

    Do you know how to change this message?

  • January 25, 2018 at 12:29 am

    Hi – interesting page thanks!

    My question for the group – assuming that PSTN conferencing access is required (and i take your point on PSTN via App users) – is there a physical limit on the number of attendees either via PSTN dial in and/or app access?

    Thanks in advance

    • January 25, 2018 at 9:59 am

      Hi Andrew,

      Thanks for the comment, and the compliment. You’re essentially talking about the maximum users a Skype Meeting can hold. Typically, a Skype Meeting can hold a maximum of 250 attendees. That goes for Skype for Business Server-based and O365-based Meetings.

      Here’s a page with the limits for meeting attendees, files, etc.: https://technet.microsoft.com/en-us/library/skype-for-business-online-limits.aspx
      It even specifies that the same maximum attendee count applies to “guests joining by phone.”

      Hope that helps!


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