Ring shaped hanging lock with replaceable core

A ring-shaped hanging lock, comprising:

• a casing with an open portion, a first opening and a second opening;
• a ring-shaped shackle with an open portion, the shackle being located within the casing, the shackle being slidable within the casing between an open position, an intermediate position and a closed position, the open portion of the shackle being aligned with the open portion of the casing when the shackle is in the open position, the open portion of the casing being closed by the shackle when the shackle is in the intermediate and closed positions, the second opening of the casing being obstructed by the shackle such that a tool cannot be inserted into the casing through the second opening when the shackle is in the open and closed positions;
• a latch which is movable between a locked position and an unlocked position, the latch being located within the casing, the latch being in the locked position and engaged with the shackle so as to prevent the shackle from moving to the intermediate position when the shackle is in the closed position, the latch being disengaged from the shackle when the latch is in the unlocked position;
• a control cam for moving the latch from the locked position to the unlocked position and for moving the shackle, the control cam being located within the casing;
• a replaceable core for operating the control cam, the core being located within the casing;
• and
• securing means for securing the core within the casing, the securing means being aligned with the second opening of the casing such that the securing means can be operated upon by the tool to permit removal of the core from the casing through the first opening when the shackle is in the intermediate position.