Codabar: устаревший штрих-код в банках крови и библиотеках
Codabar's encoding scheme, four start/stop characters (A-D), ISBT 128 successor in blood banking, and where it's still used today.
Codabar: The Legacy Barcode in Blood Banks & Libraries
Codabar is one of the earliest barcode symbologies, developed in 1972 by Pitney Bowes. Despite being technically obsolete, it remains in use in blood banking, some library systems, and FedEx airbills. Understanding Codabar helps when maintaining legacy systems or planning migrations.
Encoding Scheme
Codabar encodes 16 characters using an arrangement of 7 elements (4 bars and 3 spaces):
- Digits: 0-9
- Special characters: - $ : / . +
- Start/stop: A, B, C, D (also called a, b, c, d or t, n, *, e)
Each character has 7 elements with either 2 or 3 wide elements. The wide-to-narrow ratio is typically 2.25:1 to 3:1.
Start and Stop Characters
Codabar uses four different start/stop pairs (A/T, B/N, C/*, D/E). The choice of start/stop characters can convey meaning. In blood banking, the combination identifies whether the barcode is a donation number, component code, or blood group.
Self-Checking Property
Like Code 39, Codabar is Symbology property ensuring single print errors are detectable." data-category="Barcode Anatomy & Structure">self-checking. A single print defect cannot transform one valid character into another, providing a basic level of error protection. A Modulo 16 check digit is optional but recommended.
Blood Banking (ISBT 128 Transition)
Codabar was the standard barcode in blood banks for decades. Blood bag labels used specific start/stop character combinations:
- A...B: Donation number
- C...D: Component code
- D...D: Expiration date/blood group
The industry has been transitioning to ISBT 128 (based on Code 128), which provides more data capacity, better error detection, and international standardization. However, some blood banks still use Codabar during the transition period.
Library Systems
Many libraries used Codabar for patron cards and book barcodes. Most have migrated to Code 39 or Code 128, but Codabar labels may still circulate on older materials.
FedEx
FedEx has historically used Codabar on airbills, though newer labels use Code 128 and PDF417.
Technical Specifications
| Parameter | Value |
|---|---|
| Character set | 0-9, - $ : / . + |
| Density | Low (~10 chars/inch) |
| Self-checking | Yes |
| Check digit | Optional (Mod 16) |
| Quiet zone | 10X minimum |
Migration Recommendations
If you maintain a Codabar-based system, plan migration to Code 128:
- Code 128 is denser (smaller symbols for the same data)
- Mandatory check digit provides stronger error detection
- Broader scanner support and future-proof
- ISBT 128 (for blood banking) provides international standardization
During migration, many systems support dual-barcode reading, scanning both Codabar and Code 128 simultaneously until all legacy labels cycle out.