When a credit card transaction is sent across the network to the processor one part of the data transmitted is the POS Entry Mode, which is a code that tells the processor how the transaction was captured.  Here is a list of the code:

POS Entry Mode

• 01 – Manually keyed (this will pertain to Visa internet transactions as well)
• 02 – Magnetic stripe read (general or track 2)
• 05 and 95 – Contactless chip card
• 06 – Magnetic stripe read (Track 1)
• 07 – Contactless chip card using Visa Smart Debit / Credit chip data rules
• 81 – Manually keyed e-commerce (Mastercard only)
• 90 – Entire magnetic stripe read and transmitted
• 91 – Contactless chip transaction originated using magnetic stripe data rules (visa only)

All those mentions of Track 1 and Track 2 magnetic stripes is a bit confusing – see Wikipedia for an explanation: credit card magnetic stripes.