There are 4 LEDs on the front of the reader and a buzzer to indicate the progress of a transaction.
Card read successful – If a card read is successful, the reader will beep once after the transaction is processed. For contactless transactions, the reader provides a sequential flashing display of the yellow, green, and red LEDs.
Card processing error – All lights on the reader will turn off to indicate the contactless interface is not acceptable for a given transaction.
-For magstripe and EMV transactions: Single beep immediately.
-For contactless transactions: Two beeps, followed by a sequential flashing display of the yellow, green, and red LEDs.