An apparatus for determining andor monitoring at least one process variable. Respective compressed word frequencies may be obtained based on the respective word frequencies such that the distribution of the respective compressed word frequencies has a lower variance than the distribution of the respective word frequencies. Then, since a first area A1 and a second area A2 are divided by a partition wall 273 in the terminal block 20, it is possible to individually charge a charging resin 29A for blocking a through-hole A22 and a charging resin 29B for blocking a boundary portion between the terminal member 23 and the resinous portion 21. Each spacer forms an interface such that adjacent ferromagnetic layers produce different spin symmetry. The memory items are accumulated in a file at the client and in a backup at the device storage mirror database, and are restorable to the client from the backup.