Describes the polling for proximity cards or objects (PICCs) entering the field of a proximity coupling device (PCD); the byte format, the frames and timing used during the initial phase of communication between PCDs and PICCs; the initial Request and Answer to Request command content; methods to detect and communicate with one PICC among several PICCs (anticollision); other parameters required to initialize communications between a PICC and PCD; optional means to ease and speed up the selection of one PICC among several PICCs based on application criteria; optional capability to allow a device to alternate between the functions of a PICC and a PCD to communicate with a PCD or a PICC, respectively. A device which implements this capability is called a PXD.