Magnetic stripe
The layer for verifying magnetic stripes as defined in the ISO/IEC 7811 series — magnetic characteristics in Parts 6 and 2, recording technique in Parts 4 and 5. Even after the move to EMV, the stripe remains in live use for fallback, transit, fuel, gift and loyalty.
What this layer verifies
Testing a magnetic stripe divides into two different problems: the quality of the physical magnetic signal and the content of the data being read. Which of the two you need to confirm determines the equipment required.
| What you want to confirm | Method | Product |
|---|---|---|
| Whether the card's magnetic signal is within specification, covering amplitude, jitter and bit density | Measure a physical card | Mag-Tester REVO |
| Whether the terminal handles particular track data correctly | Generate the magnetic signal electrically | B2 magnetic stripe simulator |
How Tracks 1, 2 and 3 differ
A magnetic stripe has three tracks. In payments, Tracks 1 and 2 are the ones actually used.
| Track | Recording density | Character set | Main use |
|---|---|---|---|
| Track 1 | 210 bpi | Alphanumeric; 6 data bits plus parity, giving 7-bit characters | PAN, cardholder name, expiry date and service code |
| Track 2 | 75 bpi | Numeric; 4 data bits plus parity, giving 5-bit characters | The most widely referenced in payments. PAN, expiry date and service code |
| Track 3 | 210 bpi | Numeric; 4 data bits plus parity, giving 5-bit characters | Intended for rewriting. Largely unused in payments |
The service code indicates whether the card carries a chip, whether online authorisation is required and so on. When checking EMV fallback behaviour, how this value is handled is the key point.
High and low coercivity
This is a difference in coercivity. High coercivity, around 2750 Oe, resists magnetic disturbance; low coercivity, around 300 Oe, is easier to rewrite but erases more readily. Payment cards are usually high coercivity and short-life tickets low coercivity. If the encoder output setting does not match the card's coercivity, the card may be written but not read. This pairing is one of the things a physical card quality check confirms.
Relationship to EMV fallback
Fallback is the behaviour of switching to the magnetic stripe when the chip cannot be read. What is permitted differs by scheme and by acquirer, and fallback can be an entry point for fraud, so the terminal's branching has to be confirmed against the specification. A magnetic stripe simulator is the component that generates the track data used in fallback testing. Verifying the whole sequence from a failed chip read through to a magnetic stripe transaction needs a separate test environment covering the terminal's state transition conditions and the host's fallback permissions.
Where it is still used
Beyond POS and ATMs, the magnetic stripe remains in use in the following areas.
- Fuel and fleet — bespoke formats carrying the vehicle number and driver ID
- Gift and loyalty — bespoke BINs outside the payment schemes
- Transit and access control — magnetic tickets and legacy membership cards
Certification testing compared with development debugging
The magnetic stripe is not normally subject to a terminal type approval process of the kind used for EMV Level 1 and Level 2. Card quality, encoding quality, personalisation and conformance to each payment system's own requirements do, however, still have to be confirmed. Testing at this layer centres on quality control of the issued card and the acceptance checks on the terminal side, through UAT and debugging. Sampling during the issuance process calls for physical measurement; changes to the terminal or the host call for comprehensive testing by simulation, including invalid cases.