Platform alteration

AUTHOR: Inavate

Stockholm Central station has overhauled its audio and paging system, replacing an outdated and unsupported system with a MediaMatrix solution. Anna Mitchell talks to contractor and consultant to discover the reasons behind the decision.

When Banverket, a Swedish railway authority, turned to Sten Ranwald of Ljud och Säkerhet it marked the beginning of a ten year relationship that would see Ranwald travel the length of the country updating and handling audio systems for about 160 Swedish stations.

“It all started with Gothenburg [station] ten years ago,” recalls Ranwald. “I had no contract [with Banverket] at that time but they awarded me the job because I had done networks for the company before and they liked my work. After working on about four or five stations in Sweden they wanted to make a formal agreement with me but, under Swedish law, they had to [put the tender] out to the open market and offer all contractors the same opportunity. I answered the tender and got the contract.”

Ranwald’s contract is up at the end of October next year. But, until then, as the only contractor in Sweden handling sound installations at stations, he’s a very busy man. He travels about 60,000km a year and has so far overhauled about 100 stations, leaving 60 to go.

For many years the loudspeaker systems in most of the stations relied on a custom-made system from a Swedish engineering company, the HT90 system. It was reliable and completely sufficient when installed but today is totally outdated. Furthermore, the company no longer exists so service, spares and extensions are no longer available.

Banverket, eager to find new solutions for their paging needs, turned to Ljud och Säkerhet and requested something contemporary, with increased sound quality and built on standardised solutions with a high degree of adaptability. Ranwald settled on MediaMatrix paging systems and drafted in Patrik Eriksson from distributor, Svensk Musik TTS as consultant on the system.

Ranwald claims the he chose the MediaMatrix solution as it was a complete system that provided lots of opportunities and lots of possibilities to integrate all existing systems and create new ones. He says: “I put all the demands to TTS and asked them could you manage this? Could you fix this? [Eriksson] sat down for a couple of days then answered me… ‘yeah, we can do it’. So I went with MediaMatrix.”

The first major station where Ranwald installed MediaMatrix was Stockholm Central. “They had very specific demands on the functionality,” said Eriksson. “We proposed an ordinary ControlMatrix/ MediaMatrix system with paging consoles and gooseneck microphones. However, for different reasons they demanded their existing telephone-based paging controller system was to remain. Also, our new system had to be controlled using the very same interface as the older HT90 system; DTMF. There was also an option to use their ancient signalling interface with four-wire for audio, and a series of apocryphal pulse sequences on two separate positive-grounded control lines, but as we didn’t want custom electronics needed to interface to the NION, we went with the DTMF commands.

“Effectively, the NION on Stockholm Central is acting as a HT90-emulator, with vastly enhanced DSP capacity to care for EQ, AGC, scheduling of speaker levels (-10dB attenuation in the night) and so on. Later on, they did come back and wanted to try out the ControlMatrix concept, so at the moment the MediaMatrix at Stockholm C is a split personality; it has a complete ControlMatrix with only one PCU console running in parallel with the ordinary system. Preparations have been made so we can switch over to an exclusive ControlMatrix operation if and whenever they wish to.

“The system is made up of a MediaMatrix NION n6 and a bunch of CAB4 with an assortment of I/O cards. Communication with the existing telephone and switchboard paging system is made using a telephone hybrid. The ‘experimental’ ControlMatrix part is a Q-host without MessageNet, a CAB8i, a PCU2100 and a PCU2.”

Eriksson says that the company was presented with a problem due to the Swedish telephone standard. “We do not drop the line voltage on hook, (mostly, we reverse voltage) so the hybrid itself could not detect when the call was terminated. This was solved by programming the switchboard computer to end call with “#”, which is encoded by the NION, which then sends an RS232-command to tell the hybrid to close the line. Some logic and delay functions make sure the DTMF-commands are not forwarded to the speaker outputs.”

The speaker system was also overhauled but with an interesting twist. Although Renkus-Heinz Iconyx IC16 and IC8 loudspeakers were discreetly installed, the station owners wanted to keep the original Community horns for aesthetic and historical purposes. The Iconyx units are fed via CobraNet and driven by a rack of QSC 100V ISA 300, 500 and 800 amplifiers.

“Cobranet was the only logical way to distribute the signal in Stockholm, I think,” says Ranwald. “They had the fibre infrastructure when I arrived so I just patched into it. One of the greatest owners of networks in Sweden is the railway company so that that makes life much easier for us.”

With Stockholm completed, there was still no rest in sight for Ranwald. He continued his partnership with TTS and Eriksson to complete similar projects at Malmo Central and Gothenburg Central. At Malmo staff requested they use telephone headsets instead of goosenecks and the request was answered with a change to the PCU2 consoles. Furthermore, the station decided it wanted a Bosch Praesidio unit to handle voice evacuation although MediaMatrix still took care of paging and traffic information with signals fed into the Bosch at specific termination points.

MediaMatrix NION n6 DSP and ControlMatrix Q-host
QSC ISA series amplifiers
Renkus-Heinz Iconyx IC16 and IC8 and CobraNet-boxes.