is illustrated in fig2 4 fig2 is a top view of an identification card 207 that includes an rfid circuit comprising chip 101 and antenna 203 as can be seen antenna 203 also comprises legs 204 and 206 a button 205 is also included as is connected with or comprises a switch mechanism configured to connect legs 204 and 206 when the button is in the closed position and to disconnect them when the button is in the open position fig3 is a diagram illustrating card 207 with button in the open 205 position and fig4 is a diagram illustrating card 207 when button 205 is in the closed position antenna 203 is tuned with button 205 or more specifically the switching mechanism in the closed position such that legs 204 and 206 are connected or more specifically in electrical communication and acting as part of antenna 203 thus the impedance matching between chip 101 and antenna 203 must be designed to take into account the impedance of antenna 203 when the switching mechanism and legs 204 and 206 form part of antenna 203 as a result of the tuning of the impedance match when the switch mechanism is open there will be an impedance mismatch between chip 101 and antenna 203 the amount of impedance mismatch can be made to vary as required by a specific implementation to ensure that there is no unauthorized access to chip 101 for example in one embodiment the impedance of antenna 203 as seen by.