A transaction system includes a portable electronic token and an external read/write unit which communicate by inductive coupling. The read/write unit transmits short pulses of an r.f. carrier when in its dormant or stand-by mode and, upon detecting the presence of a token, switches its r.f. on continuously to power up the token and conduct a transaction. Thus, the system conserves power but can react rapidly when a transaction is necessary.

A portable electronic card or token has a plurality of discrete electronic components mounted on a flexible substrate, the substrate and the components are encapsulated in a plastics material, and at least one respective high tensile member is associated with each component and disposed such that a region of the card or token encompassing the component is restrained from flexing. The flexing substrate forms resilient hinge portions between adjacent components.