Data entry device comprising: a housing (102,103) formed of at least two housing portions (102,103); data entry circuitry located within the housing (102,103); at least one case-open switch assembly, operative to sense an opening of the housing (102,103); and tamper indication circuitry, operative to receive an input from said at least one case-open switch assembly, to provide an output indication of possible tampering with said data entry circuitry located within said housing (102,103), the at least one case-open switch assembly including: at least one arrangement of electrical contacts arranged on a base surface, said at least one arrangement including a central contact and at least one contact (174,176,178) spaced from and at least partially surrounding said central contact; and at least one element, having a conductive contact surface including a central contact engagement portion and at least one contact engagement portion spaced from and at least partially surrounding said central contact engagement portion, wherein the central contact engagement portion is configured to contact the central contact and at least one of the at least one contact engagement portion is configured to contact at least one of the at least one contact (174,176,178) and defines a short circuit between said central contact and the at least one of said at least one contact (174,176,178) only when said housing (102,103) is closed. a housing (102,103) formed of at least two housing portions (102,103); data entry circuitry located within the housing (102,103); at least one case-open switch assembly, operative to sense an opening of the housing (102,103); and tamper indication circuitry, operative to receive an input from said at least one case-open switch assembly, to provide an output indication of possible tampering with said data entry circuitry located within said housing (102,103), the at least one case-open switch assembly including: at least one arrangement of electrical contacts arranged on a base surface, said at least one arrangement including a central contact and at least one contact (174,176,178) spaced from and at least partially surrounding said central contact; and at least one element, having a conductive contact surface including a central contact engagement portion and at least one contact engagement portion spaced from and at least partially surrounding said central contact engagement portion, wherein the central contact engagement portion is configured to contact the central contact and at least one of the at least one contact engagement portion is configured to contact at least one of the at least one contact (174,176,178) and defines a short circuit between said central contact and the at least one of said at least one contact (174,176,178) only when said housing (102,103) is closed. at least one arrangement of electrical contacts arranged on a base surface, said at least one arrangement including a central contact and at least one contact (174,176,178) spaced from and at least partially surrounding said central contact; and at least one element, having a conductive contact surface including a central contact engagement portion and at least one contact engagement portion spaced from and at least partially surrounding said central contact engagement portion, wherein the central contact engagement portion is configured to contact the central contact and at least one of the at least one contact engagement portion is configured to contact at least one of the at least one contact (174,176,178) and defines a short circuit between said central contact and the at least one of said at least one contact (174,176,178) only when said housing (102,103) is closed.