To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

4,5
Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
Live Statistics
English Articles
Improved in 24 Hours
Added in 24 Hours
Languages
Recent
Show all languages
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.
.
Leo
Newton
Brights
Milds

From Wikipedia, the free encyclopedia

4B3T, which stands for 4 (four) Binary 3 (three) Ternary, is a line encoding scheme used for ISDN PRI interface. 4B3T represents four binary bits using three pulses.

Description

It uses three states:

  • + (positive pulse),
  • 0 (no pulse), and
  • − (negative pulse).

This means we have 24 = 16 input combinations to represent, using 33 = 27 output combinations. 000 is not used to avoid long periods without a transition. 4B3T uses a paired disparity code to achieve an overall zero DC bias: six triplets are used which have no DC component (0+−, 0−+, +0−, −0+, +−0, −+0), and the remaining 20 are grouped into 10 pairs with differing disparity (e.g. ++− and −−+). When transmitting, the DC bias is tracked and a combination chosen that has a DC component of the opposite sign to the running total.

This mapping from 4 bits to three ternary states is given in a table known as Modified Monitoring State 43 (MMS43). A competing encoding technique, used for the ISDN basic rate interface where 4B3T is not used, is 2B1Q.

The sync sequence used is the 11-symbol Barker code, +++−−−+−−+− or its reverse, −+−−+−−−+++.

Encoding table

Each 4-bit input group is encoded as a 3-symbol group (transmitted left to right) from the following table. Encoding requires keeping track of the accumulated DC offset, the number of + pulses minus the number of − pulses in all preceding groups. The starting value is arbitrary; here we use the values 1 through 4, although −1.5, −0.5, +0.5 and +1.5 is another possibility.

MMS 43 coding table[1]
Input Accumulated DC offset
Hex Binary 1 2 3 4
0 0000 + 0 +   (+2) 0−0 (−1)
1 0001 0 − +   (+0)
2 0010 + − 0   (+0)
3 0011 0 0 +   (+1) − − 0   (−2)
4 0100 − + 0   (+0)
5 0101 0 + +   (+2) − 0 0   (−1)
6 0110 − + +   (+1) − − +   (−1)
7 0111 − 0 +   (+0)
8 1000 + 0 0   (+1) 0 − −   (−2)
9 1001 + − +   (+1) − − −   (−3)
A 1010 + + −   (+1) + − −   (−1)
B 1011 + 0 −   (+0)
C 1100 + + +   (+3) − + −   (−1)
D 1101 0 + 0   (+1) − 0 −   (−2)
E 1110 0 + −   (+0)
F 1111 + + 0   (+2) 0 0 −   (−1)

This code forces a transition after at most five consecutive identical non-zero symbols, or four consecutive zero symbols.

Decoding table

Decoding is simpler, as the decoder does not need to keep track of the encoder state, although doing so allows greater error detection. The 000 triplet is not a legal encoded sequence, but is typically decoded as binary 0000.

Ternary Binary Hex Ternary Binary Hex Ternary Binary Hex
0 0 0 N/A N/A − 0 0 0101 5 + − − 1010 A
+ 0 + 0000 0 − + + 0110 6 + 0 − 1011 B
0 − 0 0000 0 − − + 0110 6 + + + 1100 C
0 − + 0001 1 − 0 + 0111 7 − + − 1100 C
+ − 0 0010 2 + 0 0 1000 8 0 + 0 1101 D
0 0 + 0011 3 0 − − 1000 8 − 0 − 1101 D
− − 0 0011 3 + − + 1001 9 0 + − 1110 E
− + 0 0100 4 − − − 1001 9 + + 0 1111 F
0 + + 0101 5 + + − 1010 A 0 0 − 1111 F

See also

Other line codes that have 3 states:

References

  1. ^ "Wired Communications T-SMINTO 4B3T Second Gen. Modular ISDN NT (Ordinary)" (PDF) (Data sheet). Version 1.1. Infineon. November 2001. PEF 80902.
This page was last edited on 9 June 2019, at 12:24
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.