logixpro 500 dual compressor simulator

I am doing the Logixpro 500 simulator for exercise 2 using dual compressors. I can get the dual compressors to swap but am now needing to have them alternate every 15 seconds. I have added timers for each compressor but cannot get them to swap. Any help please ?

look up flip flop logic

Lets say you have timer A and B, when timer A start you start compressor A and stop compressor B and viceversa when starting timer B, obviously timer A and B are mutually exclusive.

Hey ! Hey ! Hey! Thank you