Abstract: Apparatus for obtaining limited access to a given function in response to the entry of a preselected code sequence. A plurality of preselected code sequences are generated by the apparatus and compared sequentially with an entered code sequence. In the event that a generated code sequence has a preselected degree of coincidence with the entered code sequence, the desired function is enabled. A plurality of functions may be controlled by the same apparatus. Alternatively, a plurality of different code sequences may be employed to enable the same function while the apparatus individually monitors which code sequence is used to enable the function. In a preferred embodiment, the function being controlled is a fluid dispensing pump which is enabled by any one of a plurality of entered code sequences while the amount dispensed through the use of each entered code sequence is monitored individually. Provision is made for the collective and individual alteration of code sequences within the generated code sequences.