Abstract: A system is provided for unlocking a lock comprising: an electronic locking core (1) for insertion in a lock body (18), and a separate power source (40). The locking core (1) comprises: a casing (12) housing an electronic circuit board (20), and a motor (26). The motor (26) is configured to move a locking member (28) located at one end of the casing (12) and externally thereof that transitions a latch of the lock between a locked and an unlocked configuration. A terminal (56) is located at the opposite end of the casing (12) to receive power from the separate power source (40). The power source (40) is housed within a cartridge (42) separate from and connectable to the locking core (1), the cartridge (42) including a co-operating terminal to connect the power source (40) to the electronic circuit board (20).