Electronic devices can be provided with at least one first circuit component coupled to a first circuit board, at least one second circuit component coupled to a second circuit board, and a mating assembly coupled to the boards for holding them in a vertical stack. The circulator amplifies the signal from the antenna and the signal received from the device such that a twice-amplified signal is directed to the antenna. The rolled papers are installed in the rolled paper accommodation units correspondingly to the conveyance reference positions. According to one aspect of the invention, the method enables a user, typically a medical professional, to initiate, with minimal input, certain diagnostic tests involving observing and analyzing a series of QRS complexes 130, some of which are biased with a subpacing current, and others of which are unbiased. The method does not cause a significant degradation to the sample stream.