This generator is more complete than the previous one, being able to generate pulses as indicated in the table next to the diagram. In the original, a 556 was used which is a double 555.
For reference only, this is the second IF amplifier stage of a common transistor radio from the...
The L3 coil is what basically determines the resonant frequency, around 1 MHz, in this oscillator found...
This is one of many twin-T oscillator configurations that can be found in this section and on this...