HomeMatic HM-Sec-Key Montage- Und Bedienungsanleitung Seite 18

Note that to attain the household insurance, the cylinder is not to protrude
on the outside to ensure that it cannot be pulled. It must either be flush
in (unable to be dismantled from outside) the door fitting or covered by a
rosette.
The lock cylinder must have emergency and hazard functionality (double
cylinder). That means that it must be able to be opened with a second key
from the outside whether a key is inserted from the inside or not.
Some lock cylinders are not to be replaced by the resident. This occurs e.g.
in large apartment complexes that have special lock cylinders. In this case,
your key will not fit in the neighbors lock but the caretaker can open all
doors with a single "Master key".
If in doubt, ask your landlord whether you can replace the lock cylinder or not.
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Lock cylinder spacing.
1 - Inside door fitting
2 - Rosette
3 - Screw for fastening the lock cylinder in the mortise lock
4 - Lock cylinder
A Inside dimension
B Outside dimension
C Inside dimension + addition protrusion (8mm to 15mm, ideal is 10mm)
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