Transaction system

A transaction system enables a portable token to cooperate with a fixed terminal. The token is inductively coupled to the terminal, and receives data from the terminal via a frequency modulated carrier signal. Data is sent from the token to the terminal by amplitude modulation of the carrier signal from the terminal, e.g. by modulating the power drawn by the token from the terminal. The power needed to energise the on-board processing capability of the token is also obtained from the terminal via the inductive coupling. The token includes an arrangement for commencing processor operation in an orderly manner when it is brought into the proximity of a terminal, and for providing an orderly shut down when the token is withdrawn.