This pair cycle through all the combinations of input. The outputs are aligned with another P240 gun to show clearly when the detector detects the input. A Stack is a memory device which can theoretically store any number of values. In the push cycle all the values on the stack move one cell way from the control end of the stack and a new value is added into the now empty cell at the control end. In a pop cycle the value at the control end is removed and all the values move one cell towards the control end ready for the next cycle.
Control signals pass up each side of the stack.
The reflecting reaction between two gliders is used to trap the cell values between two opposing glider streams. This stack cell is designed for 3 value gliders in each cell in parallel. The value gliders cycle round in 120 generations. In order for the control signal for the Push Operation to arrive in time to open the stack cell for value gliders to enter, the value gliders must be delayed. The result is that each stack cell is slightly offset from its neighbours.