             // Could not update machine credits - attempt to save credits to card again!
             card.credits = current_credits;
             updateAndVerify(addr, card);
+            Serial.write('F'); // finish communication
             BEEP(4);
           }// else {BEEP(1);}
         } else {

    // Request and read data from other party
    Serial.write(command);
    while (!Serial.available()); // Wait till other side transmits a C
    if (Serial.read() != 'C')
      return;
    number = rfid_raw_read();
    if (recieve_error == 0) { // Received correctly, return value

      // Attempt to add credits to card
      if (updateAndVerify(addr, card)) {
        // OK Beep
        Serial.write('F'); // finish communication
      } else {
        // Reset credits on vending machine
        rfid_transmit('S', credits_in_machine);
