In reference to the physical appearance of an electromagnetic pulse as it is displayed on a monitor (oscilloscope). The pulse characteristics displayed include amplitude (i.e., signal strength) on the vertical axis, frequency (i.e., the number of cycles per unit time) on the horizontal axis, and phase (i.e., relative measure of position). Power requirements, co-interference, signal attenuation, spectral efficiency, and other considerations often require that pulses be shaped within certain minimum and maximum amplitude and frequency boundaries. As examples, T1 and ISDN pulses must fit a shape template to comply with standards. See also amplitude, attenuation, frequency, interference, ISDN, phase, power, pulse, spectral efficiency, and T1.