A medical apparatus configured to generate, without multiple electrodes, a signal corresponding to electrical impulses of a heart, and to display a waveform of that signal, comprising: a pulse unit comprising sensor(s) for receiving a single channel pulse signal waveform from a live tissue and for generating a digital pulse signal； a memory buffer； one or more processors configured to constantly apply a derivative function to the digital pulse signal and initiate a display signal to display a waveform of the derivative function during a period of time, wherein the waveform of the derivative function has a shape of an ECG signal waveform of the subject taken during the period of time, wherein the derivative function includes ΔP(t)/Δt, wherein P represents the pulse signal waveform and t is a time variable； and a digital display or printer device configured to display or print the waveform. Multiple channel embodiment also included.
