Products · Mitel
Mitel OpenScape 4000: support, maintenance and upgrades
Mitel OpenScape 4000, formerly HiPath 4000, is the proven PBX from Siemens and Unify that is now part of Mitel. We provide OpenScape 4000 support and maintenance, upgrades and modernisation, and connect it to Teams, Mitel CX and Workflow Studio.
We usually start with a simple inventory of your PBX, licences and integrations.
About Mitel OpenScape 4000
One PBX for both IP and TDM
OpenScape 4000 handles digital and analogue extensions (TDM), wireless on-site phones (DECT) and SIP in the same system, so you can modernise at your own pace. According to Mitel, it suits organisations with a few hundred to 12,000 users per system, and up to 100,000 in a network.
OpenScape 4000 is a hybrid system that combines proven features with new ones. It is used in all kinds of organisations, such as hospitals, manufacturing plants, power stations, railways, airports, large ships and banks with trading systems.
The platform was formerly called HiPath 4000 and has its roots in the Siemens Hicom 300. Siemens’ PBX business became Unify, which Mitel acquired in 2023. The latest version is V11, and it can run on Unify’s EcoServer or virtualised on VMware, Proxmox, Hyper-V and Nutanix.
We have worked with the platform since the Hicom days, from version 1.0, and are authorised for OpenScape (formerly Siemens and Unify, now Mitel). We explain how long a version receives fixes, and what that means for you, in the guide on the PBX lifecycle.
Last updated 25 October 2026.
At a glance
- IP, digital, analogue and DECT in the same system
- Up to 12,000 users per system
- Latest version V11
- Standby system, also at another site
- Branch survivability
- Works with Teams, Mitel CX and Workflow Studio
Support
Support and maintenance for OpenScape 4000
We support OpenScape 4000 in all versions, including older HiPath 4000 systems. If you have an older version, we can upgrade it so that it receives Mitel’s fixes again.
What’s included
- Fault reporting and troubleshooting, with remote access that you control
- Contact with Mitel when a case needs escalating
- Changes to the PBX, such as extensions, groups and permissions
- Mitel’s security fixes, applied according to a plan
- Software Assurance and your licences with Mitel
- Regular reviews of the PBX and a plan for the next step
We describe what a support contract should include in the guide PBX support contracts.
Fault reporting
Report faults as set out in your support contract, which also states the hours that apply. No contract with us yet? Call +46 8 730 66 00 or email info@icomserv.com.
How we help you
What we do with Mitel OpenScape 4000
Upgrades
From V10 to V11, with checks of licences, Software Assurance and integrations.
New hardware or virtualisation
Older hardware is replaced with EcoServer or virtual servers.
Teams
Via Direct Routing and an SBC, which the PBX connects to over SIP. The SBC protects the traffic between your network, your operator and Teams.
Contact centre and automation
Mitel CX and Workflow Studio on top of the PBX, without replacing it.
Step-by-step modernisation
Group by group to SIP, and at a later stage to OpenScape Voice or another platform if it suits you.
Support takeover
If another provider has looked after your PBX, we take over support with a plan and a parallel period, as part of our third-party PBX maintenance.
Use cases
How Mitel OpenScape 4000 is used
Old and new phones side by side
Digital phones and SIP work in parallel, and groups move at their own pace.
Teams for the office, the PBX for the rest
Users make calls in Teams, while DECT, alarms and analogue devices stay on the PBX.
Contact centre with Mitel CX
Voice and digital channels in the same queues, on top of OpenScape 4000.
Branches that keep working during outages
Branches and remote cabinets keep working if the main system or the link to it goes down.
From your own hardware to virtual servers
The same PBX and the same numbers on new or virtual servers.
Switchboard
Switchboard operators work in the AC-Win attendant console, linked to presence and directories.
Works with
- Microsoft Teams via Direct Routing and SBC
- Mitel CX (requires OpenScape 4000 V11)
- Mitel Workflow Studio
- OpenScape Voice and OpenScape Business
- SIP trunks, ISDN and QSIG
- DECT, the AC-Win attendant console and Xpressions voicemail
What we review first
- Current version and hardware
- Software Assurance status
- Extensions by type: digital, analogue, DECT and IP
- Branches and survivability requirements
- Integrations: contact centre, attendant console, alarms and Teams
- Plans for SIP and Teams
How we work
From the first conversation to day-to-day operations
01
Discovery
We review how you work today, which systems you have and what you want to achieve.
02
Proposal
You receive a concrete proposal covering technology, timeline and cost, and we explain our choices.
03
Implementation
We install, integrate and test, and we train your users and administrators.
04
Operations and support
After go-live, we stay with you for support, updates and further development.
Common questions
Frequently asked questions about Mitel OpenScape 4000
What happened to HiPath 4000 and Unify?
It is the same product line. HiPath 4000 became OpenScape 4000, and Unify, formerly Siemens Enterprise Communications, was acquired by Mitel in 2023. The platform is now called Mitel OpenScape 4000.
Can we mix old digital phones and SIP?
Yes. Digital and SIP work in parallel, and user groups can move at their own pace.
Do wireless DECT phones work with OpenScape 4000?
Yes. OpenScape 4000 can run wireless DECT phones in the same system as desk phones, and DECT from Ascom, for example, can be connected to the PBX over SIP. We look after both the DECT system and the connection. Read more about Ascom DECT.
Does OpenScape 4000 work with Teams?
Yes, via Direct Routing and a certified SBC, which the PBX connects to over SIP.
What happens in the branches if the link goes down?
With local gateways and emergency mode in the branches, local calls keep working.
Can OpenScape 4000 run virtualised?
Yes, on VMware, Proxmox, Hyper-V or Nutanix, or on Unify’s EcoServer.
Do we lose our licences if we move to OpenScape Voice later?
Mitel states that licences can be transferred within the OpenScape family. We confirm what applies in your case in our quotation.
Further reading
Guide
Upgrade or replace your PBX?
Decision support for organisations that run MX-ONE or OpenScape today.
Solution
PBX migration
From an old PBX to a new platform or Teams, step by step, with a rollback plan for every stage.
Guide
Teams and your existing PBX: coexistence and gradual migration
How to let Teams and your PBX work together while you move at your own pace.
Product
Mitel OpenScape Voice
The SIP platform for large and distributed environments, with redundancy.
Solution
Third-party PBX maintenance
Keep the PBX that works. We take over support for MX-ONE, OpenScape and OmniPCX Enterprise and keep your PBX up to date with the manufacturer’s security fixes.
Guide
PBX lifecycle and end of life: extending its life safely
What manufacturers’ lifecycles mean, and how to keep your PBX secure for many years to come.
Third-party PBX maintenance
Start with an inventory
Do you have an MX-ONE, OpenScape or OmniPCX Enterprise? We usually start with a simple inventory of your PBX, licences and integrations, free of charge. You then know where you stand, and we can give you a quote for support, operations or replacement.