A radio receiver includes a power control module for selectively powering down and powering up radio receiver elements in between known communication periods according to one aspect of the present invention. The parameter applier is configured to apply a phase shift to the downmix audio signal to obtain a phase-shifted version of the downmix audio signal, while leaving a decorrelated signal unmodified by the phase shift. The detector provides for a significant increase in security for a two-way QKD system over the prior art that employs a conventional detector such as a photodiode. The processor may operate in a low power mode based on a clock signal generated from a low power oscillator. A common electrode is on the CCF layer.