Quad distribution

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In telephone and telecommunication cables , the copper cores are usually stranded in pairs. Often two pairs are twisted into a foursome .

Star quad

Star quad
Star quad is z. B. used for microphone signals

A star quad is a stranding element for copper wires. Four wires are twisted together to form two cross-twisted twin wires. Opposing cores each form a pair. The perpendicular position of the wire pairs to one another results in the desired high crosstalk attenuation .

In Germany and most European countries, the local telephone networks are built up with bundled star fours in underground or aerial cables. Twisted pair cables are used in the UK and USA .

The structure of the star quad must be so mechanically stable that the wires maintain their symmetrical position to each other over the entire length, otherwise the crosstalk behavior deteriorates. In the case of lines for high operating frequencies, additional support and stabilization elements are therefore sometimes used.

In ADSL and other xDSL applications, conventional telephone cables in star-quad stranding (e.g. J-YY) are operated in frequency ranges for which they were not originally designed, which leads to unfavorable crosstalk behavior in the quad. This does not apply to 2-pair cables, since the symmetry of the quad is guaranteed here. If several xDSL connections are transmitted over a cable with more than one star quad, separate quads are chosen to reduce crosstalk.

Typical applications of the star quad are e.g. B.

  • high quality microphone cables
  • Telephone underground cables
  • some telephone installation cables, e.g. B. J-YY, or U72 (Switzerland), 2-pair telephone cable JY (St) Y or F-vYDvY (Austria)

Advantages of the star quad over twisting in pairs

  • Higher packing density (→ smaller cable diameter)
  • Lower operating capacity (→ lower attenuation )
  • Phantom switching possible (transmission of a third speech circuit via a quad. This technology is hardly of any importance today).

Twisted Quad Cable

Twisted-Quad (Star Quad) is the English name for star quad . The expression is z. B. used in network cables to distinguish them from common twisted pair cables .

The wires can have a common sheath, which can comprise a braided or foil shield.

The twisted quad cable has a line structure that corresponds to that of the twisted pair cable. The designations are UTQ (Unshielded Twisted Quad) instead of UTP (Unshielded Twisted Pair). Twisted quad cables are available for all standardized frequency ranges and for all categories.

Dieselhorst-Martin stranding

Two twisted pairs
Fernkabel Berlin-Hanover (1914) 52 twin cores stranded in 26 Dieselhorst-Martin four-core for 78 speech circles

The Dieselhorst-Martin stranding (after the inventors William Dieselhorst and Arthur William Martin) is a special, outdated quadruple ( DM quad ) and is only of historical importance. It was used (almost exclusively) in Germany by the post office, railways and the military, and in district and long-distance cables of the post office until around the 1970s. Since the late 1930s in the remote telephone network have become increasingly carrier frequency equipment used and coaxial cables laid. The DM quad has no advantage over the star quad when it comes to carrier frequency transmission.

With DM stranding , two twisted pairs with different pitch lengths were stranded to form a four. The purpose was to optimize phantom switching in multi-pair underground cables. While the operating capacity of the two pairs is added in the star-quad phantom circuit , the capacity and thus the attenuation is lower with DM stranding in the phantom circuit. However, the disadvantages predominated (costly production, approx. 15% larger cable diameter).

Count quad

In telephone cables according to the ÖVE standard, which are made up of many fours, exactly one foursome has an a-line with a different color for each layer. These so-called counting quads are used - with a defined direction of the line - to systematically count all four of a cable and thus identify them.

literature

Remarks

  1. Rheinlandkabel , bayern-online.com, accessed May 16, 2012
  2. ^ Dieselhorst-Martin stranding, patent GB190312526 : Improved Manufacture of Electric Cables.
  3. ^ History of telecommunications until 1999 - Kurznachrichten 1936 , bayern-online.com, accessed May 16, 2012
  4. Bernhard Deutsch: Elektro Nachrichtenenkabel , Erlangen 1998, page 40
  5. Meinhart - cables and wires. Catalog 2009. accessed June 9, 2017. pp. 184–188 and "Core identification of telecommunication cables according to ÖVE" p. 262.