Abstract: Optical card reader systems are known in which an optically encoded card is read to provide an output signal. However, in known systems, the card has to be presented in a particular orientation. Described herein is a card (80) which has three code zones (85, 86, 87), the upper zone (85) carries a code in one of its data streams from which a series of clock pulses is derived to assist in the processing of the data in the streams of the zones (85, 87) or (86, 87). Zones (85, 87) carry identical data presented in identical fashion. In order to determine the presentation of the card, start words (83, 84) can be utilised to indicate to the reader which way up and which way round the card is presented.