In telecommunication, a two-out-of-five code is a 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).

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:

Deux parmi cinq

Barcodes