Linear Products Knowledge Base

Decoding a Card

Select Set up: Access Control: Utilities: Card Decoder.

On this page you can:                                                                                        

1. Decode the bits on Wiegand formatted cards.
2. Decode the bytes on Track 2 of Magstripe cards.

Wiegand access cards typically contain a stream of bits that encode the facility code and the encoded card number. The card format specifies the total number of bits, the parity bits, which bits are the facility code, and which are the encoded number.

Magstripe cards typically contain a stream of bytes on Track 2 that encode the facility code and the encoded card number. The card format specifies the total number of bytes, the Start and End Sentinels, a field separator, and a checksum character. These bytes will be represented in ASCII characters.

1. A Start Sentinel byte is indicated with the ASCII value ";".
2. A Field Separator byte is indicated with the ASCII value "=".
3. An End Sentinel byte is indicated with the ASCII value "?".

If you do not know the format of the existing card population you can discover it using this utility.

Note: The more you can learn about the card format before you try this process the easier this process will be. Any information you can obtain such as facility code value will facilitate this decoding process.

To decode a population of Wiegand cards:

1. Obtain 5 to 10 sample cards from the existing card population.
2. Select a card format from the Card Format drop-down list. Wiegand 26 bit format is the most popular so try that first. The numbered bit positions displayed across the top of the page to the right will be color coded based upon the card format selection. Facility code bit positions are shaded green. Card ID bit positions are shaded purple.

Note: In the Format Data column the Facility Code Start Bit, Bit Length, and the Facility Code value boxes (green background) will fill with the values for the selected card format. The Card ID Start Bit and the Card ID Bit Length boxes (purple background) also fill with the correct values for the selected card format.

3. Select a reader for reading sample cards from the Reader drop-down list.
4. Read several of the sample cards and the bit streams from these cards will appear on the right side of the page under the bit position numbers. Bit Length, the total number of bits on the card, is displayed on the far right under the Bit Length column.

Note: In the Card Data column the Facility Code and Encoded # boxes (orange background) will fill with the values from the selected card read. These values are calculated based upon the bits designated by the selected card format as representing the facility code and the card ID number.

5. Now comes the hard part. You must examine the bits from each card to discover patterns that will tell you the format of the card.
6. Depending upon the patterns that you see you may need to alter the Facility Code Start Bit or the Facility Code Bit Length. You may also need to alter the Encoded # Start Bit or the Encoded # Bit Length.
7. Once you have correctly set the facility code and encoded number start bits and lengths you can create a card format to match the card population by clicking the Save Format button.
8. This will take you to the Card/Keypad Formats page. Enter a Name for your format and click Save.
9. For Facility code of ‘0’ place a hyphen (-) in the bit definitions from the Facility Code Start bit through the Facility code Bit Length.