An analog BBD echo gadget (bucket brigade device)
Here is the circuit of an analog delay device, so a simple echo device:
Delay times of up to approx. 50mS can be set. For larger values, an MN3208 can be used instead of the MN3207. However, this one has a different housing and another pin assignment. Even longer delay times can be achieved by connecting several MN3208s in series.