PRI connection via ISDN

Provider & price overview for PRI


Savecall knows the market and works together with all carriers. We find the best solution for your network.


A PRI connection, or S2M is an ISDN interface.

By definition, it always consists of at least 16 and no more than 30 use channels, a D channel and a synchronization channel, each with 64kbit/s, totaling 2048kbit/s.

Usually, this connection is provided via a 2Mbit/s dedicated line, a so-called E1 and is ideal for companies larger than 20 employees who want or need to ensure continuous and permanent availability.

Benefits of PRI

Best voice quality

since an uncompressed channel isn’t always available for every conversation.

Lowest failure rates

in comparison to other connection types, ISDN is error-free

Nationwide availability

via regulating wide-coverage availability

PRI Connection via ISDN

When changing providers, you can take your existing numbers with you which is called porting.When you initially commission a PRI connection, you will receive a number from the number pool of the provider you have chosen. You will then be assigned a number block from 0-499 or 5-999.

When ordering several PRI connections, it is possible to obtain a number block from 0-999.

If you only order one PRI ISDN connection, but to not want to do without a large number block, we recommend order the block from 0-99 and adding the last extension to via your TC system.

In addition, in contrast to other technologies, a wide variety of features and options are available to you that only work with ISDN (e.g. a postage meter).

If you still have a TC system that is equipped with a PRI ISDN interface, you can decide between a few providers depending on the location.

We can inform you about which of these providers offer this and what has to be taken into account, such as the question of how long ISDN will still exist.

Utilize our independent expert consulting to find the right provider for your company or directly check the availability for your location using our online check. We will gladly assist you!

Features of a PRI via ISDN

ISDN is fully standardized. And still you have additional services that are largely only supported by ISDN:

  • Inner-office call routing
  • Fee indicator during and after the call
  • Call number display and suppression
  • Fax transmission and transmission of the signals for postage metering machines and doorbells/openers.

In addition, there are special flat rate models or negotiated minute models, online tools that make it easier and more transparent for you to display invoices.

ISDN Disaster Recovery

If telephony is critical for your company, one of the following two scenarios can help you ensure continuous telephony reliability:

  • Back-up: two PRI connections with the same number can be provided via two different routes. In this case, one of the two lines can be capped if it fails, but you can still make calls via the second route.
  • Disaster Recovery: in a K case, depending on the extension, all of the phone numbers are routed from location a to another PRI connection at another location B, whereby several escalation levels are defined in order to ensure resumption of operations as fast as possible within a few minutes.

Overview of all PRI via ISDN providers

Provider Product
Colt Colt Voice Line
Colt Telekom primary multiplex connection
versatel Versatel VT line
ecotel Ecotel voice-direct primary multiplex connection
Vodafone Vodafone primary multiplex connection

Costs for PRI via ISDN

The standard PRI connection from the Telekom costs 260.76€/month, net.

There are other providers on the market who can provide you the same connection, depending on the following factors:

  • Location: Depending on the location of your company, there are several providers to choose from.
  • Providers: If you have several providers to choose from, we will check the current offers since they each have different terms and conditions.
  • Duration: It is also better for the provider of your choice if you want to use its services for a longer period of time. In this case, there is certainly the option of negotiating the conditions for the base fees.


Andreas MarreckAndreas Marreck

ICT Expert

Tel: +49 (0)89 / 219 914 810


© 2020 Savecall telecommunications consulting GmbH