The present invention provides a security module having a communication interface being capable of operating according to any from a selection from a plurality of predetermined operation modes or communication protocols. The security module further comprises a voltage detector to detect the voltage on the module's power supply connection. Depending on the value of the detected voltage or to which of a plurality of predetermined voltage ranges the detected voltage may be categorized, the security module is made to function according to one from the plurality of predetermined communication protocols. According to an embodiment of the present invention the plurality of communication protocols require that the security module operate at a plurality of different frequencies.