DSL splitter

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A DSL splitter (Engl. To split : split, split), and splitter , DSL Soft or BBAE ( broadband access equipment , broadband access unit ), is a device that a single trunk for the simultaneous use of an analog telephone ( or ISDN ) and DSL broadband Internet . For this purpose, the frequencies of telephone and DSL , which are transmitted together over a subscriber line (TAL), are divided in the receiving direction and merged in the sending direction. A splitter is required at both ends of the subscriber line.

So-called All-IP connections (also called Next Generation Network ), which enable telephony via an Internet connection, can be implemented without splinters and then use the low frequency ranges for additional transmission capacity.

Features and functions

Opened DSL splitter from 1999 with manual switch (blue) between ANALOG ( Annex A ) and ISDN ( Annex B )

From an electrical point of view, a splitter is a crossover network . The high-pass filter component for connecting the DSL modem is only rudimentarily designed as a capacitive coupling (one capacitor each with 27  nF and 400  V in series in the two lines that lead to the DSL modem), while the low-pass filter circuit for connecting conventional landline - terminals or ISDN NTBAs is realized substantially more complex.

In Germany, the 4B3T line code is used for ISDN connections on the local loop ( U K0 interface ) , which means that frequencies between 0 and 120 kHz are used. Frequencies above 138 kHz can then be used for DSL ( Annex B ). For analog telephone connections, frequencies below 25 kHz are usually used, so frequencies from around 25 kHz (channel 6) can be used for DSL from a technical point of view ( Annex A ), which enables higher ranges and data transmission rates to be achieved. For reasons of mass production, simpler operating technology and, in particular, marketing reasons (no worse position for ISDN), Deutsche Telekom only uses splitters for Annex B for analog and digital telephone connections in Germany. Outside of Germany, for example in Slovakia , splitters for Annex A are used everywhere on analog telephone connections.

In the local exchange , the splitter is not designed as a separate device, but rather integrated into the circuitry on the circuit board of a DSLAM or permanently installed as a so-called MDF-integrated splitter in the main distributor .

An analog connections outside Germany instead of the here discussed splitter technique is a different frequency filter topography usual: There, a high-pass filter is connected upstream of the DSL modem, or that is already integrated in the modem, and before any (usually parallel -connected to the modem) analog terminal is a low-pass filter switched. This type of frequency filter installation is also possible on analog connections in Germany (a splitter can also be used as a simple low-pass or high-pass filter), but it may result in a reduced quality of the DSL signal due to the resulting stub lines .

A circuit diagram for a DSL splitter can be found in Figure 5 of US Pat. No. US6728367. In the meantime, less complex filter circuits are also available for VDSL requirements.

connections

Two different generations of splitters: 2002 (right) and 2005 (left)
Opened Splitter (Generation 2005)

The following three sockets are located on a splitter common in Germany:

  • An RJ socket for connection to the TAE socket with the help of the cable supplied (as with the NTBA), where contacts 1 and 6 are assigned to office a / b. If the TAE cable supplied is too short, a longer installation cable can be used instead and connected directly to the terminals Amt a / b of the splitter. A cable with twisted wires should then be used, longer flat cables should be avoided.
  • An NFN- TAE socket for connecting analog telephones, fax machines, answering machines and modems.
  • An “ RJ-45 ” socket (modular socket 8P2C), on which contacts 4 and 5 are assigned DSL a / b.

Alternatively, it can also be connected directly to the terminal strip:

Terminal block of a modern splitter (Germany)
Office TAE DSL
a b La Lb W. b2 a2 a b
  • Office a / b is the input of the exchange line ( subscriber connection line ), these terminals are parallel to the RJ socket
    • Note: If the splitter is connected directly to the subscriber connection line and thus assumes the function of the first TAE , it should be ensured that it is a model with an integrated passive test termination (PPA) and that this is switched on, since without this a line test is performed during a Fault is not possible
  • TAE terminals are used to connect the NTBA (with an ISDN connection) or analogue end devices (telephones, telephone modems, fax machines, etc.) directly
    • La and Lb : If no AMT line is applied to the splitter, La and Lb can be used as inputs to the TAE socket of the splitter
    • If the AMT-line use, it is sufficient, as a rule, the analog devices via the terminals La and Lb to connect
    • If analog terminal devices are connected simultaneously via both the TAE sockets of the splitter and via the terminal strip, then terminals a2 and b2 should be used instead to avoid a parallel connection
    • If a telephone (F socket) is plugged into the TAE socket of the splitter, it must be ensured that the contacts to a2 and b2 are interrupted and all subscribers from a2 and b2 can no longer be reached. Only a few devices with an N connector (e.g. fax or analog modem) can be plugged into the TAE socket of the splitter if additional devices are to be connected to a2 and b2 , as the contacts themselves are internally in standby mode bridge and only open when active. However, this does not work with many modems built into computers.
  • DSL a / b are parallel to the "RJ-45" ​​socket, forwarding to the router / DSL modem
    • the DSL a / b connections of the splitter are connected to the middle contacts (pins 4 and 5 of the "RJ-45" ​​socket) with the DSL modem / router
    • the connection between the splitter and DSL modem / router should use a twisted pair cable ( twisted pair carried)
    • Untwisted flat telephone cables must be avoided at all costs for reasons of electromagnetic compatibility
    • in a star quad , two opposing cores form a pair

For the function of a telephone it is irrelevant whether a splitter is installed. Neither the installation of the splitter before the DSL provision nor the lack of it after the DSL provision affect the operation of an analog or ISDN telephone connection.

literature

Web links

Commons : DSL splitters  - collection of images, videos and audio files

Individual evidence

  1. ↑ VOGT electronic Aktiengesellschaft: DSL switch . Patent dated November 11, 2004.
  2. ↑ embodiment ADSL VDSL splitter (PDF; 155 kB), June 2012 Design.