Based on looking at the datasheet for the pt2399 delay chip.
You can see the output which moves in triangle wave fashion always trying to match the input.
Uses a latch to sample the result of comparing input with the output of an integrator.
Basically the circuit looks at the output, if it is lower than the input a "1" is generated which is sent to the integrator, via an inverter, pushing the output upwards. If output is higher than than the input a "0" is generated which is sent to the integrator, via the inverter, pushing the output higher.
If the data stream is saved, or delayed, it can be used to drive a similar integrator to re-create the signal.
In real life, not advised to use op amps as comparators.
