1. Schematic

As with any oscillator, no input is needed. It swings by itself. 

For example: decreasing capacitor C1 to a 10 nF value would lead to a tenfold increase of the frequency. 

2. Functional description

The first OP stage is an integrator (negative feedback loop), the second a non-inverting Schmitt trigger (positive feedback loop).

The wave is triangle shaped on the integrator output (IC pin 1) because the capacitor is forced to charge linearly: the current through resistor R1 is constant and the input of the OP Amp draws (virtually) no current.

The gradient x (V/ms) is calculated by the following formula (U_s would be 9V here):  

R2 and R3 determine the voltage thresholds (therefore the oscillator frequency) of the Schmitt trigger.

No reset switch for the integrator is needed, for it is part of a more extensive device (i.e. oscillator).

3. Power supply

A symmetrical power supply is needed, here realized either thru an additional OP arrangement consisting of an UA741, or simply thru two 9V blocks.

4. Application

The oscillator could be part of a sound generator/synthesizer.

A triangle signal generates a very distinctive, not too unpleasant sound - triangle signals consists solely of odd harmonics: 1st, 3rd, 5th, etc..