A slave device for receiving frames wirelessly transmitted from a master device , the frames being of a first and second type and having a common preamble, the frames of the second type having a preamble extension prior to the common preamble, the frames being wirelessly transmitted from the master device at a known periodicity and within a known time frame, the slave device comprising: a processor configured to maintain the slave device in at least one low powered mode relative to at least one higher power mode, and periodically sets the slave device in a higher-powered mode to receive and process the frames of the first or second type wirelessly transmitted from the master device ; and a slave clock ; wherein the processor is configured to: based on the slave clock , set the slave device in a higher-powered mode in a period prior to an expected wireless transmission of the common preamble of each frame from the master device to detect a preamble extension of a frame of the second type in the period; return the slave device to a low powered mode when no preamble extension is detected in the period; and control the slave device to wirelessly receive information from the master device and/or wirelessly transmit information to the master device when a preamble extension is detected in the period, and return the slave device to a low powered mode after the information has been wirelessly received and/or wirelessly transmitted; wherein the processor is configured to detect the preamble extension by identifying a predefined sequence of symbols in the preamble extension. a processor configured to maintain the slave device in at least one low powered mode relative to at least one higher power mode, and periodically sets the slave device in a higher-powered mode to receive and process the frames of the first or second type wirelessly transmitted from the master device ; and a slave clock ; wherein the processor is configured to: based on the slave clock , set the slave device in a higher-powered mode in a period prior to an expected wireless transmission of the common preamble of each frame from the master device to detect a preamble extension of a frame of the second type in the period; return the slave device to a low powered mode when no preamble extension is detected in the period; and control the slave device to wirelessly receive information from the master device and/or wirelessly transmit information to the master device when a preamble extension is detected in the period, and return the slave device to a low powered mode after the information has been wirelessly received and/or wirelessly transmitted; wherein the processor is configured to detect the preamble extension by identifying a predefined sequence of symbols in the preamble extension. based on the slave clock , set the slave device in a higher-powered mode in a period prior to an expected wireless transmission of the common preamble of each frame from the master device to detect a preamble extension of a frame of the second type in the period; return the slave device to a low powered mode when no preamble extension is detected in the period; and control the slave device to wirelessly receive information from the master device and/or wirelessly transmit information to the master device when a preamble extension is detected in the period, and return the slave device to a low powered mode after the information has been wirelessly received and/or wirelessly transmitted; wherein the processor is configured to detect the preamble extension by identifying a predefined sequence of symbols in the preamble extension. <EOS>