Example embodiments relate to a security device having two communication interfaces sharing at least one pin, each interface being capable of operating according to either of two predetermined communication protocols. The security device may further include a frequency detector to detect the frequency of a clock signal on the shared pin. Depending on the value of the detected frequency, and to which of a plurality of predetermined frequency ranges the detected frequency pertains, the security device may function according to one of the two predetermined communication protocols, operating at two different frequencies.