Reminder: PSTN end of life in 2025

Openreach are in the progress of moving all customers from the old analogue public switched telephone network (PSTN) to a fully digital network: Openreach puts the stopper on copper | Openreach – this means no more ISDN or analog copper lines, fiber is the way forward.  As of September 2023, Openreach are only provide digital phones across the UK: Retiring the copper network | Openreach.

Jisc can assist with your move from On-premises PSTN or even SBC based services to a cloud solution.  We have the Jisc Session border controller and a professional service offer for moving to a Teams Phone System.

How does a modern SBC fit in?

An SBC (Session border controller) is a piece of hardware that takes a voice call and routes it to a PBX (Telephony Exchange).  In the modern world this tends to be a cloud-based SBC rather than physical.

Jisc’s SBC is hosted in our Slough data centre using a carrier grade redundant pair, with excellent support via the familiar Jisc Service Desk.  It is still charged on a concurrent calling basis, compared to the industry move to a more per user basis, along with capacity flexing for clearing and exam results days, provides excellent cost efficiencies, keeping money available for educating.

Teams Direct Routing Overview
Teams Direct Routing Overview

The Jisc SBC can be used with any telephony service (zoom/etc) but being the Senior M365 architect here at Jisc I’d be remised to not promote Teams Phone System.

Teams Phone System

If you are already a M365 organization, adding Teams Phone System to your could be as easy as connecting the SBC (if you are on A5) or procuring an add-on license.  Microsoft does offer multiple ways of connecting Teams to the PSTN

Teams PSTN Connectivity Options
Teams PSTN Connectivity Options

The easiest, but most expensive, is Microsoft Calling Plans, these range from £2 per user per month upwards; Operator connect is the next on the list, this is where you use a major provider (e.g. BT/Vodaphone) and their SBC to link into Teams, this can range price wise but is still charged at the per user per month model; the older method and most cost efficient is the Direct Routing (hosted) option and this is where Jisc’s SBC sits.

Whilst we would recommend moving away dedicated handsets towards headsets, Teams does support a wide compatible SIP enabled handsets which are ideal for refuge areas: Plan SIP Gateway – Microsoft Teams | Microsoft Learn, allowing you to save money, and for headsets improve the hygiene of your phone system (where headsets are not being shared).


Moving from your on-premises infrastructure to cloud base solution is perfect for most organizations wishing to avoid the Capex of new hardware as well as reducing the overall cost of ownership.  Teams Phone System can be a very cost-effective solution if you are already heavily invested in M365 and is one of the sector leading telephony services.

Figure 1: Y23Q4 Magic Quadrant for Unified Communications as a Service, Worldwide

Drop your relationship manager a message and arrange an SBC/Teams Phone System scoping call today to look at your options.

Note: Teams Phone System and SBC can be utilized independent of each other.

Note 2: Speak to your lift provider about mobile cell connections rather than using SBC services.

By Nick Brown

Senior M365 Developer and Architect @ Jisc Cloud Solutions.
Find me on twitter @techienickb

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