A mobile telephone can be used with a data recording system for storing the voice data or other data contents of telephone calls, whereby contents of telephone calls performed using the mobile telephone (101) can be stored on a memory card as a data record, which can be transmitted from a computer (109) via a computer network (108) and gateway (107) to be stored by the telephone conversation recording apparatus (106) in an identical way to the contents of a call performed using an internal telephone (105). A user can thus utilize or process the contents of a recorded telephone call in the same way, irrespective of whether the user has performed the telephone call at a remote location using a mobile telephone or by using an internal telephone.