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Figure 1 Study 1. Electrode positions on the thorax (1–6), and electrical current vectors (a–k) for the encircling overlapping waveform. The thorax is represented as a circle with the heart in the middle. Vectors a, c, e, g, i and k result from an electrical pulse generated by a single-capacitor discharge and flowing between a single pair of electrodes (e.g., electrodes 1–4, pathway 1). Electrical pulses 4, 5 and 6 flow between the same electrode as pulses 1, 2 and 3 but are reversed in polarity. Vectors b, d, f, h and j result from the overlapping discharge of two capacitors yielding pulses flowing between two pairs of electrodes simultaneously (e.g., 1–4 and 2–5), with the mean electrical vector lying between the two pathways defined by the two electrode pairs. Each electrical vector is of equal duration. The damped sinusoidal and biphasic shocks were always given utilizing pathway 2 (pads 2–5).