A water-hammer proof and silent check valve comprises a shell, a spring, a flow guide body and a cowl. Dielectric materials may be used to reduce conductivity between the two stacks. The apparatus also includes multiple sampling circuits configured to sample the input signal at different taps in the branches of the delay line and to output sampled values. Subcarriers of different frequencies or waveforms can be used to add channelization of impulse radio signals. In the relaxed configuration, a portion of the guide tube is able to assume the shape or curve defined by the controllable distal portion of the endoscope. The templates and documents generated are designed to closely resemble a paper chart.