There isn't a direct equivalent for a flip flop in AB but with the use of a one shot instruction, you can do essentially the same thing. If you are conversant in AB here's how you would do it: In your first rung, add an input (XIC, examine if closed or an open contact) and tag it for your "switching" and add an OSR output. The OSR is a one shot (rising) that you will add two tags to. The first is the storage bit, this is merely a bit that AB uses to keep track of the OSR status, maybe name it RUN_ONS_STORAGE. The second tag to enter is the one shot output bit (we'll call it RUN_ONS). Add another rung with and XIC tagged to your one shot output bit, RUN_ONS, an XIO (examine if open or normally closed contact) and give it your output address (say, RUN_CMD) and an OTE (output enable or a coil) and tag the output to RUN_CMD. Add a branch around the two inputs and add an XIO tagged RUN_ONS, and an XIC tagged RUN_CMD. That is how to create code that will work similar to the flip flop. Of course, you don't have the set or reset dominant options but there could be some code work around there as well. Hope that helps.