Circularly averaged binned amplitude (top) and phase (bottom) as functions of projected baselines in kλ. Only the visibilities for Elias 29, TMC1A and L1527 are shown as indicated in the top of each panel while the visibilities toward the GSS30 sources are shown in Appendix A. The standard error of each uv bin, which is smaller than the symbol size, is plotted and the expected zero-signal amplitude is also indicated by the red dashed lines. The expected zero-signal amplitude for Elias 29 is more than a factor of 10 lower than the signal.