Abstract: An anti-theft system for construction machines, comprising a memory which stores, as machine-side identification information, first identification information allocated construction machine by construction machine and second identification information allocated in common to plural construction machines, a first collating medium having the same identification information as the first identification information, a second collating medium having the same identification information as the second identification information, a collator which collates the identification information of the first or the second collating medium with the machine-side identification information, and an operation controller which cancels the inhibit of operation of the construction machine concerned when there is obtained a coincident collation result by the collator. With this anti-theft system, an owner of construction machines can manage the construction machines by only one type of a collating medium while preventing theft.

Abstract: The prevent invention provides an oil filter comprising a filter element housed in a casing, the filter element being formed of two or more cylindrical element pieces piled on top of another in the height direction and attachably and detachably connected through connecting members. Accordingly, the efficiency in each of manufacture, stock control and storage of the filter element can be improved, and the cost can be also reduced.

Abstract: An anti-theft system for construction machines, comprising a memory which stores, as machine-side identification information, first identification information allocated construction machine by construction machine and second identification information allocated in common to plural construction machines, a first collating medium having the same identification information as the first identification information, a second collating medium having the same identification information as the second identification information, a collator which collates the identification information of the first or the second collating medium with the machine-side identification information, and an operation controller which cancels the inhibit of operation of the construction machine concerned when there is obtained a coincident collation result by the collator. With this anti-theft system, an owner of construction machines can manage the construction machines by only one type of a collating medium while preventing theft.