Abstract: A lockable cassette 10 for valuable papers can be inserted into a housing 20. The cassette is closed and locked when removed from the housing, and when inserted therein can be unlocked by electrical activation and opened to access the papers provided that the electrical activation is effected in accordance with a pre-set program. For this purpose there is provided a locking arrangement which includes a programmable memory (171), a comparison circuit (172), and a logic circuit (173). The memory is accessible for programming and is arranged to feed a series of pulses to the comparison circuit, which in turn compares them with a series of pulses fed-in from without to the locking arrangement. The logic circuit blocks the opening of the locking arrangement in the absence of agreement between any two pulses. This blocking of the opening function is not noticeable externally until the whope series of pulses has been compared.