There are two PT2399 delay chips in series with independent delay time controls on the X and Y axis of the "TIME" joystick(Left). The delay-mix and feedback-amount are controlled together by the "ECHO" knob. The "REGEN X2" switch enables the output from delay-chip 1 to be fed back to its input, as well as to delay-chip 2's input. When disengaged, only delay-chip 2 will have feedback(echo).