MagTek TTL - Manual (Page 7)

Section 1. Decoding Reader Output
3
TRACK 1 DATA FORMAT
The following is typical for Track 1 data.
The Track 1 data format includes the following items:
1.
Approximately 62 leading clocking zeros
2. The Start Sentinel "%"
3. Up to 76 alphanumeric characters selected by the user
4. The end sentinel "?"
5. The LRC (longitudinal redundancy check character)
6. Trailing clocking zeros (minimum of 62) to the end of the card
Each data character is in a 7-bit (6 plus parity) alphanumeric format. The data is in the format
"parity, 32, 16, 8, 4, 2, 1". Parity is odd (an odd number of "one's" in each character).
The character is written "backwards" on the card starting with the least significant digit and
ending with the parity bit. The card data format is "1, 2, 4, 8, 16, 32, parity".
See Appendix C for ATM and credit card formats.
Example: The data message "AT3" is encoded on the card as follows:
1.
"000..00" leading clocking zeros (approximately 62)
2. "1010001" the Start Sentinel "%" (1000101)
3. "1000011" the character "A"* (1100001)
4. "0010110" the character "T"* (0110100)
5. "1100100" the character "3" (0010011)
6. "1111100" the End Sentinel "?" (0011111)
7. "0011100" the character "<"** (0011100) the LRC (check digit)
8. "000..00" trailing clocking zeros (minimum of 62) to end of the card
*Use capital letters only.
**The character "<" is not defined by credit card standards but is a legitimate LRC character.
The binary values of all card data can be found in the MagTek publication, Application Note -
Character Conversion, Part Number 99875065, see Appendix A.
See Appendix C for ATM and Credit Card Formats.