Abstract: A transaction system comprises a plurality of components each performing a respective function, the components being interconnected by a serial data bus. Each component can initiate an information exchange operation with any other component. A component may transmit a message consisting of either a general instruction for causing the component receiving the message to carry out one of a plurality of different types of operations depending upon the nature of the instruction, or a message in the form of a direct memory access request identifying a specific location in a memory of the receiving component to which data is to be written or from which data is to be read.

Abstract: A coin validator checks the measured properties of a tested item against stored ranges to determine whether the tested item is acceptable. Individual sets of ranges can be enabled and disabled, and switched between narrow and wide ranges, in a teach mode of the validator. Selection of the ranges to be enabled, disabled or switched is accomplished by causing the validator to test an item to determine its type.

Abstract: A coin mechanism comprising testing devices for testing coins as to their acceptability, a substantially upright coin store or tube adapted to contain a plurality of acceptable coins of a particular denomination up to a predetermined upper level, and a coin dispenser for dispensing coins from the lower end of the store. The coin store is provided with a coin inlet located below the predetermined upper level, and devices for delivering acceptable coins of the denomination from the testing devices through the inlet into the store. This enables the coin store to be pre-loaded to the upper level and, when its contents have been partly dispensed, to be refilled from the coin tester, through the coin inlet at the lower level.