Sinusoidal frequency changes are con verted into proportional d-c volthage and fed into pulse amplifier and integrator to generate constant-amplitude triangular waveform for measuring dynamic linearity of amplifier as function of frequency. Schmitt trigger con verts input sine wave to constant-amplitude square wave. Frequency sensor produces d-c voltage proportional to frequency to serve as d-c source for pulse amplifier and integrator.-D. E. Cottrell, Frequency Sensor Stabilizes Triangular-Wave Generator, Electronics, 37:9, p 38-40.