Question about BDTR-2H chip

Hello Im trying to understand how does the BDTR-2H chip works.
I understand that there are 3 delay units that make the reverb, but I dont understand how the circuit works, what is that Osc and how the 3 PT2399 are connected to each other. Can anyone help me ?

Thanks!

The PT2399 chips delay the audio signal.

From **broken link removed**:
The PT2399 is a single chip echo processor IC utilizing
CMOS technology. Which accept analog audio input
signal, a high sample rate ADC transfer the analog
signal into a bit stream then storage to internal 44Kbit
RAM, after processing the bit stream will de-modulate
by DAC and lowpass filter. Overall delay time is
determined by internal VCO clock frequency, and user
can easy to change the VCO frequency by changing
the external resistance. The PT2399 performs low
distortion (THD<0.5%@0.5Vrms) and low noise
(No<-90dBV) characteristic for audio purpose, and pin
arrangement and application circuit are optimized for
easy PCB layout and cost saving advantage.

Briefly, it converts the analog input to a digital stream, stores the stream in random access memory then reads it out some time later and converts it back into an analog signal. This happens continuously as new signal samples overwrite older samples.