Abstract: A protective switching apparatus is provided comprising in an insulating case an interruptible current path in which cooperating contacts are disposed, one of which is fixed and the other is mobile in response to the actuation of a tripping member. The mobile contact is disposed at a first end of a contact holder arm whose second end is associated with a retractable fulcrum forming the output member of the lock, the contact holder arm being subjected to the action of a resilient quick opening means and to the action of a resilient closure means. The contact holder arm is mounted without fixed fulcrum, so as to pivot either by bearing against a bearing surface of the toggle joint during tripping on a fault, or against a bearing surface of the retractable fulcrum of the lock during voluntary manual or automatic tripping.