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The Swisscom control centre in the main post office building at Bahnhofsplatz in Schaffhausen has to move - and with it all 50,000 connections. During eight night switchovers, three copper splicers and two CFS switching fitters kept their cool and an overview of thousands of wires and connections.
The control centre will need far less space in future than before with only 5,000 active copper connections left. Consequently, the extensive premises on the second floor of the post office building will no longer be required. Markus Oehler, Head of Team Network Planning, Construction & Operations summarizes the background to the night switchovers.
The Swisscom control centre in Schaffhausen, on the second floor of the post office building, directly opposite the central railway station, is home to 50,000 copper connections. Since the Schaffhausen region is already, to a large extent, connected with optical fibre, only about 5,000 of the 50,000 copper connections are still needed. Most of the 5,000 still active copper wires are used as power lines to supply power to the signal converters (mCANs) in manholes and house connection boxes.
What is an mCAN? mCANS are signal converters. Optical fibre cables are either laid to the manhole in the street (fibre to the street) or to the house connection box (fibre to the home). The signal covers the final metres from manhole or the house connection box to the flat via a copper wire - and this is exactly where mCAN comes into the picture: The mCAN converts the optical signal (light signal) that is conducted via the optical fibre cable into an electrical impulse and transfers this to the copper cable.
The control centre will need far less space in future than before with only 5,000 active copper connections left. Consequently, the extensive premises on the second floor of the post office building will no longer be required. They have now been re-let, and all Swisscom installations have to be completely removed by mid-July. From then on, the new control centre as well as the pre-existing cable gallery will be in the basement of the post office building.
The night switchovers take place once a week. As a result, the adverse effect on customers associated with the network interruption are kept as low as possible.
"The splicer team and CFS switching fitters are already on the spot on the day of the switchover at 7.00 p.m.," explained Oehler, Head of Team Network Planning, Construction & Operations. "By 11.00 p.m., the final steps are taken to prepare the night switchovers; at the same time, the first work is carried out for the following week."
The copper conductors from the old control centre are examined and illuminated in advance of the night switchover. The splice points of the cables of the new main distributor are checked out. This ensures that all existing connections between the control centre and splice point are okay before the switchover. Markus Oehler explains: "The unconnected, empty conductors can be separated in advance and 'pulled into strips'. This means the copper cables are pre-sorted."
This involves threading four conductors through one hole of a perforated strip with 20 holes each. "As a result, you later know which conductor is assigned to which number." During this work, the copper splicers have to observe a prescribed sequence of cables, called the cable order.
These preparations serve to connect the conductors correctly with each other later in the course of the switchover. Before the actual switchover can begin at 11.00 p.m., the final work preparation is performed. All splice sleeves have to be unpacked and prepared for splicing. The sleeve bottoms are fitted and placed in the right position.
"The preparations for each night switchover always take place one week in advance," explained Markus Oehler. "The switchover itself is scheduled for the period from 11.00 p.m. until 5.00 a.m." During this period, customers in part face interruptions.
The switchover of two 2,400-cables and one 600-cable is performed in the third of eight night switchovers. They are all separated and sawn off at 11.00 p.m.
The heavy cables are put into order before splicing. This means that the cables in the sleeve basement are arranged to ensure that they do not get tangled up with each other or interlaced. This guarantees free access to the cable in the event of a disruption or damage. Each of the cables contains 2,400 or 600 copper conductor pairs. The splicer team need all their might to jointly move the bulky, metre-long cables to the right position.
After the separation at 11.00 p.m., the conductors are once again connected to each other ("spliced") according to the information in the splicing table. Each of the three copper splicers works on a sleeve. This means the team is fast and efficient and gets customers back onto the network as quickly as possible. Thanks to this division of labour, the men can also be decentrally organised and observe the corona-related distancing rules.
Parallel to the splicing, the CFS switching fitters perform the transfers. As soon as part of the connections has been restored, the coordination office checks whether the mCANS that are connected to the copper cores can be reactivated (the mCAN is supplied with electricity through the copper conductors). This makes it possible to react directly to any errors.
Working on such big cables is no longer a daily occurrence and requires a certain amount of routine. The same eight fitters are used deliberately for all eight switchovers. As a result, they can work together perfectly. Reading the splicing tables, which in part are several pages long, demands all the concentration of the cablex specialists. Thanks to their outstanding, devoted commitment, it was possible to perform all of the switchovers as planned and professionally.