A trading and auction system, and a method for the authentication of buyers and sellers and for the transmission of trading instructions in a trading and auction system is disclosed. The active electrode may comprise an exposed bare wire at the leading edge of the cup. The device may be fabricated by at least partially shielding the electrical components with polymer material, followed by overmolding the polymer material with thermoplastic polymer material. Dialing the emergency telephone number enables the proximity location information to be transmitted to an emergency call center. A portion of the second signal field is modulated according to a second technique or a portion of the second long training field is modulated according to the second technique to signal to a receiver that the second data unit is formatted according to a second data unit format.