Main distributor
A main distribution frame ( MDF ), English: Main Distribution Frame short: MDF , is the central distribution of communications cabling a building or property . In the public telephone network is located in each local exchange to the main distribution of the associated "local access network".
Main distributor of the telephone network in Germany
Main distributors are located in the connection area (ASB) of a local network. Main cables are laid from the main distributor to the individual cable distributors , from which the branch cables are then laid to the individual households.
The subscriber connection lines that lead to the outside of the subscribers are connected to the main distributor of a local exchange and, if required, connected to the technical equipment of a network operator (routed). At the HVt are u. a. the analog ( POTS ) and digital ports (ISDN) of an exchange as well as connecting cables to other network operators are connected.
In addition to telephone connections , xDSL connections and leased lines are also switched on the main distributor . There are around 8,000 main distributors in Germany. The area served by a main distributor is the connection area .
Each main distributor bears the identification number of the connection area to distinguish it (e.g. HVt 35 for main distributor No. 35). In earlier times, all telephone connections that were switched via a main distributor had partially identical telephone numbers. So had z. B. all switched connections of the HVt35 a number that began with 35. This was due to the electromechanical technology. With the introduction of digital switching technology and the associated possibility of porting a number over different connection areas, this fixed connection area assignment based on the telephone number was no longer applicable.
construction
The main distributor of an exchange consists of a 3 m high free-standing steel frame to which the individual interconnection elements ("switching strips" and "separating strips") are attached. It has a "vertical side" and a "horizontal side". The separating strips are attached vertically on the vertical side, from there cables lead into the cable distribution basement of the exchange and in main cables monitored by compressed air to the cable distributors . The switching strips are attached horizontally on the horizontal side. Technical equipment such as port modules, DSLAMs and the connecting cables to other network operators are connected there.
In the case of HVts requiring less space, wall installation is available, i.e. This means that the horizontal (top) and vertical side (bottom) are combined in one control cabinet.
In some exchanges, switching strips have also been installed on the side of the “vertical” strips. These are mostly fed by network nodes that are located outside the exchange. Since, strictly speaking, these are also fed via underground cables, they must consequently be arranged on the vertical side.
In the 1970s there were also attempts in Mannheim to construct HVts only with vertical sides; this was supposed to promote the use of switching robots, but ultimately failed to gain acceptance.
At the moment there are two different forms of the main distributor: HVt 55 and HVt 71. The numbers roughly indicate the development years ( 1955 and 1971 ) of the respective components. Both types can also occur on the same HVt, as the mechanical construction of the "framework" is almost identical and only the switching strips differ. The main differences are:
- Thanks to the higher packing density of the contacts, the HVt 71 enables considerably more connection options for technology (horizontal) and main cables (vertical).
- While in the main distribution frame 55, the leads are soldered to the switching strip, they had to be in the main distribution frame 71 with solder, screw and strip the insulation piercing connecting devices ( LSA Technology ) interconnected.
In addition to the types already mentioned (whereby the 55 series is no longer being built), numerous other series are offered, for example:
- 5000 series (/ HVT 95)
- LSA + (and type variations)
- 1000RT series.
These series are still offered on the German market today. There are other products on the world market, but almost no use in Germany. The product currently most frequently used in Germany is the HVt 71.In addition to the task of establishing contact between the subscriber cables and switching cables, the main distributor often uses optional plug-in protective cassettes to protect against overvoltages and overcurrents (e.g. from lightning strikes or so-called power contacts). The DSL splitters necessary for the operation of DSL can also be accommodated in the main distributor (HVt-integrated DSL switch, English: MDF integrated splitter ).
Switching connections
To connect any line on the horizontal side with any line on the vertical side, jumper wire (or jumper wire) is routed between the two sides . Every switched line is documented in a database . There are also “ coordinates ” on the horizontal and vertical sides .
The coordinates are called row, bar, pin on the vertical side , and bay, line, switching element and pin on the horizontal side .
For example, an entry for a port (horizontal side) of 501-07-16-3 means that this is the first bay (the designations of the horizontal side are usually numbered 501+), the altitude is 7 (from counted from top to bottom), the switching strip is about the 16th switching element, and pin 3 is meant within this element. A horizontal strip usually occupies 5 bays (e.g. from 501 to 505), but there are also smaller switching strips that take up either one or one and a half bays. If a strip occupies several bays, the coordinates generally refer to the starting point; in the case of strips that fit into one bay alone, the respective bay would be specified (e.g. 503 instead of 501).
Solutions are currently being developed to automate manual maneuvering with the help of remote-controlled switching matrices . See also: Automatic switching matrix .
More functions
Test equipment (in Germany system- external test technology (SEPT) ) is also used on the main distribution board , with which both the subscriber connection line (TAL) can be measured and tested, as well as the subscriber's port on the switching system (e.g. supply and ringing voltage ). In some countries, surge arresters are also installed on the main distribution board in order to protect the switching system from surge voltages that can be brought in via the subscriber line.
See also
literature
- Oliver Rosenbaum: Expert Practice Lexicon EDP Abbreviations. Vienna 2000, ISBN 3-8169-1790-9 .
- Karl Strecker (ed.): Auxiliary book for electrical engineering. Volume 1, low-voltage output (telecommunications technology), tenth edition, Springer Verlag, Berlin / Heidelberg 1928.
- Peter R. Gerke: Digital communication networks. Springer Verlag, Berlin / Heidelberg 1991, ISBN 978-3-642-93459-9 .
- Kristof Obermann, Martin Horneffer: Data network technologies for Next Generation Networks. 1st edition, Vieweg + Teubner, Wiesbaden 2009, ISBN 978-3-8348-0449-5 .
- Ernst Hettwig, Walter Mai: Self-dialing long-distance traffic in railway telephone systems. Second expanded edition, Springer Verlag, Berlin 1944.
Web links
- Link to the domestic German HVTs in a map view
- Image collection distributor and line technology
- From the main fiber optic distribution box to the house transfer point (accessed on May 27, 2017)
Individual evidence
- ↑ Corning Cable Systems: Splitter Solution for Central Offices and Remote Cabinets ( Memento of the original from February 17, 2009 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. .
