A proximity coupling device (18, 30) is provided by a mobile phone and PICCs (tags (24, 25, 29)) of type 1 (24), type 2 (25) and type 4A/B (25). The tags (24, 25, 29) all respond to a poll request signal emitted by the proximity coupling device (18, 30) with poll response signals having a bit string characteristic of type 1 and type 2 tags (24, 25, 29) respectively. The proximity coupling device (18, 30) is responsive to reception of the bit strings to identify bit collisions in the bit strings emitted by different tags (24, 25, 29) within a radio frequency field (23) generated by the proximity coupling device (18, 30). The bit collisions enable the proximity coupling device (18, 30) to discriminate the presence of type 1 and type 2 tags (24, 25, 29) in the radio frequency field (23) and implement an efficient tag reading procedure.