Two-out-of-five code

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In telecommunication, a two-out-of-five code is a m of n code in binary-coded decimal notation in which:

1. each decimal digit is represented by a binary numeral consisting of five bits of which two are of one kind, called "ones," and three are of the other kind, called "zeros", and
2. the usual weights assigned to the bit positions are 0-1-2-3-6. However, in this scheme, zero is encoded as "binary" 01100; strictly speaking the 0-1-2-3-6 previously claimed is just a mnemonic device.

Source: From Federal Standard 1037C

The U.S. Post Office POSTNET barcode uses a two-out-of-five code printed in long bars for "ones" and short bars for "zeros" to represent the ZIP+4 code for automated mail sorting and routing equipment. The weights assigned to the bit positions are: 7-4-2-1-0 (Though in this scheme, zero is encoded as 11, or "binary" 11000). This method was also used in crossbar switching systems.

The IBM 7070, IBM 7072, and IBM 7074 computers used a two-out-of-five code. The bit positions were numbered 0-1-2-3-4, with no associated weights. The sign of a word could be A Alphameric, - Minus, or + Plus; using only bit positions 0-3-4.

The following table represents decimal digits from 0 to 9 in various two-out-of-five code systems:

Digit	Telecommunication 01236	U.S. Post Office 74210	IBM 7070, 7072, 7074 01234
0	01100	11000	01100
1	11000	00011	11000
2	10100	00101	10100
3	10010	00110	10010
4	01010	01001	01010
5	00110	01010	00110
6	10001	01100	10001
7	01001	10001	01001
8	00101	10010	00101
9	00011	10100	00011
A	N/A	N/A	1––10
-	N/A	N/A	1––01
+	N/A	N/A	0––11