Abstract The present interest in vectorcardiography and the high cost of the equipment have led to the development of a mobile vectorcardiograph which makes use of two standard direct-writing electrocardiographs and a low-priced industrial oscilloscope. The cost, excluding the two electrocardiographs, but including the camera, was about $500. A block-diagram of the vectorcardiograph is shown in Fig. 1. The electrocardiographs are connected through de-emphasis networks to the input terminals of a pair of external deflection amplifiers. The amplified signals are applied directly to the deflection plates of a cathode-ray tube (CRT). A variablefrequency sawtooth generator acts as a beam interrupter when its output is applied to the control grid of the CRT. Fig. 2 shows the complete vectorcardiograph mounted on a wagon for mobile use, with the amplifiers, beam interrupter, and power supply contained in the cabinet on the lower shelf. A camera is mounted on a hinged support over the oscilloscope screen. The circuit diagram is shown in Fig. 3; it should be noted that a smaller power supply could have been used.