一种用于确定在读取器/写入器装置，其特征在于，最初的控制单元从备用模式转移到在其中检测信号发出的检测模式的电磁场的应答器单元的存在的方法。 同时和/或随后的天线信号被窃听，其被转发到解调单元这一点，从天线信号开始，以确定一个比较信号。 该比较信号被转发到在其中它与一个参考信号进行比较的控制单元。 偏离该比较信号，以一个预定的值的参考信号中，通信信号被发送。 否则，控制单元被设置回待机模式。 该方法的特征在于包络检测器被用作解调单元从所述现有技术的不同。

A method for determining presence of a transponder unit in an electromagnetic field of a reader / writer device, wherein initially a control unit is brought from a standby mode to a detection mode in which a detection signal is emitted. At the same time and / or subsequently an antenna signal is taken, which is passed to a demodulation unit in order to determine starting in this, from the antenna signal, a comparison signal. This comparison signal is forwarded to the control unit where it is compared with a reference signal. Deviates from the reference signal of the comparison signal by a predeterminable value, a communication signal is transmitted. Otherwise, the control unit is brought back into the standby mode. The method differs from the prior art that an envelope detector is used as a demodulation unit.