Method and apparatus for detecting item substitutions during entry of an item into a self-service checkout terminal

A method of providing security during operation of a checkout terminal, with the terminal having a scale, includes the step of storing a first identification code associated with a first item in a memory in response to entry of the first item into the terminal. The method also includes the step of detecting the weight of the first item with the scale and storing a first weight value associated with the weight of the first item in the memory in response thereto. The method further includes the step of storing a second identification code associated with a second item in the memory in response to entry of the second item into the terminal. The method moreover includes the step of detecting the weight of the second item with the scale and storing a second weight value associated with the weight of the second item in the memory in response thereto. The method yet further includes the step of generating an item substitution control signal if (1) the first identification code is the same as the second identification code, and (2) the first weight value does not match the second weight value.