Patent ID: 7603090

Claim:
A circuit for a first communication partner appliance designed for contactless communication within a communication system comprising at least one second communication partner appliance in which circuit either an active send mode or a passive send mode may be activated, the circuit comprising: terminal means to transmit carrier signals usable for contactless communication; communication signal processing means to activate an active send mode and a passive send mode, wherein the active send mode uses a carrier signal generated with the communication signal processing means for the contactless communication, and the passive send mode uses a carrier signal generated with a second communication partner appliance and received by the circuit via the terminal means for the contactless communication; determination means to determine first energy source information which comprises at least one parameter of at least one energy source serving to supply the circuit with electrical energy; an external energy source information identification stage to identify second energy source information which comprises at least one parameter of at least one energy source serving to supply a circuit of the second communication partner appliance with electrical energy; and decision means to form a decision result based on the first and second energy source information from the first and second communication partner appliances, wherein the decision result influences which send mode is to be activated in the circuit of the first communication partner appliance, and wherein the decision means are designed to communicate the decision result to the second communication partner appliance with the aid of the communication signal processing means.