1. In a point of sale system for acquiring bar code data relating to a transaction, wherein a first bar code scanner is arranged to scan bar codes and provide data relating to scanned bar codes to a processor, the improvement comprising a second portable bar code scanner, said second scanner including a radio module for acting as a slave unit using a master-slave data communication protocol and said second scanner including an identifying bar code, and wherein there is provided a master radio module associated with said point of sale system and wherein said master radio module is arranged to act as a master for communication with said slave radio module in response to reading of said identifying bar code.