An electronic synthesizer is described for determination of atomic positions in crystals. The synthesizer sums the two‐dimensional Fourier series representing planar, centro‐symmetric projections of electron densities in a crystal unit cell; and the projection is presented by a television scan on the screen of a cathode ray oscilloscope. The specific advantage of the device is the immediate observability of effects on the projection of alterations in signs of one or any number of Fourier coefficients.