The changing voltage, VC, across C1 and the hysteresis, VH, of IC1A determine the duty cycle, T1/(T1 + T2), of the output waveform. VTU and VTL are IC1
Figure 2. The changing voltage, VC, across C1 and the hysteresis, VH, of IC1A determine the duty cycle, T1/(T1 + T2), of the output waveform. VTU and VTL are IC1