unknown Triangle Wave Generator

The first stage compares an input against a reference and transitions to low logic level when the input is greater than a upper level threshold. The output transitions to logic high when the input has reduced below a low level threshold. With an RC feedback filter, the circuit becomes a relaxation oscillator. The output is a square wave at 50% duty ratio. A high pass filter centers the square wave signal about zero. Finally an integrator converts the square wave to a triangular wave.