Access Control Card Formats
26-bit Card Format
The most commonly used access control card structure.| Component | Bit Count | Bit Position | Details |
|---|---|---|---|
| Leading Parity | 1 bit | 1 | Even parity over bits 2-13 |
| Facility Code | 8 bits | 2 to 9 | Values 0-255 |
| Card Number | 16 bits | 10 to 25 | Values 0-65,535 |
| Trailing Parity | 1 bit | 26 | Odd parity over bits 14-25 |
34-bit Card Format
Here’s a clear breakdown of a 34-bit access control card format, which is commonly used for systems needing more unique IDs than the standard 26-bit format allows.| Component | Bit Count | Bit Position | Details |
|---|---|---|---|
| Facility Code | 16 bits | 1 to 16 | Extended facility/site Code |
| Card Number | 16 bits | 17 to 32 | Unique user/card ID |
| Parity or Reserved | 2 bits | 33 and 34 | Optional parity or reserved use |
37-bit Card Format
One of the most common 37-bit formats is HID Corporate 1000 Format (Format #26), widely used in enterprise access control systems. It provides a significantly larger number range and stronger credential management than 26- or 34-bit formats.| Component | Bit Count | Bit Position | Details |
|---|---|---|---|
| Reserved | 1 bit | 1 | Often unused or set to 0 |
| Company Code | 12 bits | 2 to 13 | Unique to the organization (0-4095) |
| Card Number | 24 bits | 14 to 37 | Unique card ID (0-16,777,215) |