Picture shows the infrastructure of the Siemens Smart Infastructure in the form of illuminated glass models; black-and-white

Annex B Replaces Wire Shortage

The farewell to ISDN: Siemens Smart Infrastructure had to migrate around 60,000 fire alarm systems without interruption. 

Download article as PDF

A normal “fire week” in Germany: Tuesday morning there is a moment of shock at the Vinzenz of Paul Hospital in Rottweil. A fire in the cellar causes the fire brigade to be deployed on a large scale. 70 residents of the Luisenheim are evacuated. Nobody is injured. Cause of the fire is an electrically operated service vehicle. On Wednesday a fire brigade of the fire and rescue station Altona moves out to the children’s hospital Altona. Fire in the basement of the clinic. Friday morning large fire brigade operation at Marien Hospital in Bergisch Gladbach. Nobody is harmed.

Emergeny call or fire alarm system

Around 180,000 times a year, a fire brigade of around 23,700 professional, factory and voluntary firefighters is deployed. It usually only takes a few minutes for one of the more than 50,000 fire trucks in Germany to arrive at the scene of the fire. Nowhere else is the helper network in the field of fire protection as closely meshed as in Germany and Austria. When the fire brigade races to a mission, the preceding emergency call was not always made via the emergency number of the fire brigade, 112. In many cases, a fire alarm system triggers the alarm.


The picture shows Heiko Behler and Ralf Dürholz from Siemens Smart Infrastructure sitting around a table in a conversation.

Heiko Behler and Ralf Dürholz from Siemens Smart Infrastructure had to convert around 60,000 fire alarm systems throughout Germany to IP.

“The professional fire alarm systems consist of several components. The detectors on the ceilings are networked with a fire alarm centre in the building. Fire alarms are triggered here and transmitted from there to one of our two service and emergency call control centres,” explains Heiko Behler, who is responsible for fire alarm systems at Siemens Smart Infrastructure. The systems are intelligent lifesavers that have to function reliably around the clock, because each alarm lands in parallel at a fire department control centre. Within seconds, it knows where the fire is, what is burning and how many people can be in a building.

The fire alarm control panel is the most important component of the entire system. It is, so to speak, the brain of a nervous system at the ends of which the detectors hang. This is where all the messages from the installed sensors converge and trigger the previously programmed actions. In addition to making an emergency call, this can be a computer call or an announcement. The fire alarm centre is usually the first important point of contact for the fire brigade when it enters a burning building with the key stored in the fire brigade key depot.


When telecommunications providers announced that all ISDN lines would be switched to IP, most companies were unaware of what this meant. In addition to the telephone connections, they had to migrate everything to IP that had previously sent data and voice via ISDN lines, including lifts, home emergency call systems and fire alarm sy tems. Previously, these alerted the Siemens and fire brigade control centres via a permanent ISDN connection. “The automatic fire alarm takes place in two independent ways – via a landline and via mobile networks. This increases reliability. Should the landline line fail, the mobile connection will jump in,” says Behler.

Optimum time for IP conversion

From a purely technical point of view, the Siemens experts were aware of the changeover. But neither the Siemens nor the T-Systems project team had any idea what dimensions this project would take on. “We installed around 60,000 transmission devices throughout Germany between Flensburg and Berchtesgaden and ensured that they function reliably,“ explains Ralf Dürholz, who oversaw the mammoth project. “When the project was launched in April 2015, the first challenge was to take stock. For each individual system, we had to check what had to be done, whether it was already transmitting via IP or when the optimum time for the changeover would be.”

“There was no unplanned failure during the IP conversion of the approximately 60,000 fire alarm systems.”

Heiko Behler, Siemens Smart Infrastructure

Fire alarm system must always work

Not easy, because a fire alarm system should always work. If parts of a fire alarm or extinguishing system are temporarily taken out of operation or a system failure occurs, replacement measures must be planned beforehand. This can be, for example, a fire security guard or a security post, which the operator must organise on his own accord. And planned shutdowns must be notified at least 72 hours in advance to the building supervisory authority as the responsible approval authority. Behler commented, “Almost 15 months passed before we were able to change over the first device.” That was summer 2016, and there were only two and a half years left for around 60,000 systems, with an average of 700 working days and more than 85 conversions per day.

NO INTERRUPTIONS of Mobile Communications ALLOWED

“Despite the immense number, we were relatively relaxed at first. We thought we’d go to the locations and exchange things quickly,” says Dürholz, describing the good feeling “The worry came later when we realised that it wasn’t that easy after all. Nobody had any experience with how to manage such a mass of IP conversions. We weren’t allowed to interrupt a fire alarm system, but we knew that switching over at Telekom would take at least six to 36 hours. During this time, the mobile phone line was not allowed to fail.” Which can’t always be guaranteed, because if for some reason, for example because of a demonstration or an event, a lot of people are registered in a radio cell at the same time, the mobile service could collapse.

Several hundred systems per day

Picture shows luminous plastic models, which are to represent different buildings

Just putting together a team that could carry out the necessary work on the fire alarm systems was not easy. In the hot phase of the project, more than 300 Siemens service technicians worked simultaneously on the systems in six different zones in Germany. T-Systems employees were also involved. At peak times, they converted several hundred systems to IP on good days. “And if there was a problem somewhere, the colleague from the north called the colleague from the south and was given tips. That was real teamwork clear across the country,” says Behler with pleasure.

His colleague contingency also benefited from the project. For the duration of the rebuild, the technicians initially used an “interim solution, as there was a lack of cores at some locations,” reports Dürholz. “We then turned the emergency solution, called Annex B, into a permanent solution because it allowed us to modify and prepare our transmission equipment in peace before the new IP line was connected.”

IP migration in three years

A good six months after the punctual conversion of the last plant, the two Siemens project managers look back with a little pride on the project of the century. Customer for customer, the team migrated the fire alarm systems to IP over a period of almost three years. Behler reflects, “Although we had to put up with interrupting the main line, there was no unplanned failure. Only a few times were technicians too fast. At the end of each changeover, the technicians actually had to trigger an alarm for testing purposes to check that the system was working. They had to inform the fire department beforehand. A few times they have forgotten this. In such cases, the fire brigade is called out accordingly. Which actually happened.”

Contact: Markus.Obels@t-systems.com

More Information: www.new.siemens.com

More Information: www.t-systems.com

Author: Roger Homrich
Photos: Alice Backes

Do you visit t-systems.com outside of Germany? Visit the local website for more information and offers for your country.