| 摘要 |
A press-button unit has a push-rod mounted to be axially displaceable in a sleeve. An external surface portion of the push rod is provided with a groove system, with a recess and with a rib member. The rib member extends between a leading portion of the groove system and a leading portion of the recess. The press-button unit is provided with a latching element, which is accessible through an opening in the sleeve and which is capable of co-operating with the groove system to cause the press-button unit to have a latching action. The latching element is selectably positionable relative to the rib member, without even partial disassembly of the unit, to cause a portion of the latching element to enter either the groove system or the recess so that - in dependence on the selected setting of the latching element - the press-button unit is selectively operable either with or without latching action.
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