Abstract: When using a magnetic alternating field to prompt portable electronic tickets, such as smart cards, it is important that the prompting is effected reliably and independent of the position thereof. In order to generate an essentially isotropic magnetic alternating field over a set time interval, one embodiment of the invention involves the use of an antenna array comprising two or three frame antennas. A switching unit supplies, in a sequentially alternating manner, a unit of information to each of the frame antennas so that a quasi-isotropic magnetic alternating field, which is considered over the period of time, is radiated by said frame antennas. This results in reliably prompting tickets that are located in the surrounding area of the antenna arrays.