Technician Handbook ! 673 Electronic & Computer Controlled Systems Basic Operation An oscilloscope has test leads similar to a DVOM. The leads are connected in a circuit where you want to measure a signal. When operating, the scope draws a line, or trace , across the display screen corresponding to the voltage it is reading. As voltage increases or decreases, the line moves up and down the screen as it is traced. To keep the line from going off the top or bottom of the display screen, a vertical control adjusts the voltage scale so the trace stays on-screen. A similar control adjusts the time scale . 36 Technical Training