A method of acquiring the identity parameters of two or more mobile devices (20), the method comprising: obtaining a list of two or more base stations (1, 2, 3); and acquiring identity parameters from the devices (20) by emulating each base station in the list. Two or more base stations may be simultaneously emulated, and the list of two or more base stations may be obtained by simultaneously interrogating two or more base stations (1, 2, 3). The identity parameters may be IMSI and/or IMEI and/or TMSI codes.