Abstract: A system for locking objects for a predetermined time on the basis of prepayment. A central processing unit (1) is connected to a plurality of object-locking devices (27) which may be locked after prepayment has been made into said unit. During count-down of the unit (1) to zero the object-locking devices can be unlocked for access, but only once. When the count-down continues below zero unlocking is prevented until additional payment has been made.The System is particularly appropriate as a parking system for bicycles, a system for locking washing machines in laundromats, and a system for lockers at bus and railroad stations and at airports.