Patch Codes do not contain any encoded data. Instead, the pattern of the code tells scanning software which specific action to perform. There are six Patch Code patterns:
- Patch 1 — Wide, wide, narrow, narrow. This is used for post-scan image control.
- Patch 2 — Wide, narrow, narrow, wide. This code assigns “image level 2” to the scanned document.
- Patch 3 — Wide, narrow, wide, narrow. This code assigns “image level 3” to the scanned document.
- Patch 4 — Narrow, wide, wide, narrow. Patch 4 is used for post-scan image control.
- Patch 6 — Narrow, narrow, wide, wide. This Patch Code is also used for image control.
- Patch T — Narrow, wide, narrow, wide. Also known as the “transfer patch,” this code assigns a predefined image level to the next scanned document.
Although Patch Codes may be placed on all four corners of a document, only one is read. The extra codes ensure that even if documents are scanned upside down or rotated, at least one Patch Code is still readable. While code functions can be customized, Patch Code patterns 1, 4, and 6 are generally used for color or multi-feed document detection, while pattern 2 is used for document separation, pattern 3 is for batch separation, and pattern T can be used for either.