Alternating pumps

OSF catches the end of each demand. A toggle rung flips LeadB, and LeadB picks the pump for the next demand.

Step by step

Pick a step. The rungs are drawn by the editor after Core scans the program up to that step.

Global.Demand

Global.Swap

Global.LeadB

Global.Swap

Global.LeadB

Global.Demand

Global.LeadB

Global.PumpA

Global.Demand

Global.LeadB

Global.PumpB

1. Demand on. LeadB is 0, so PumpA runs.

Step	Demand	Swap	LeadB	PumpA	PumpB
1. Demand on	1	0	0	1	0
2. Demand off	0	1	1	0	0
3. Scan 3	0	0	1	0	0
4. Demand on	1	0	1	0	1
5. Demand off	0	1	0	0	0
6. Demand on	1	0	0	1	0

OSF passes power for one scan when Demand turns off, so Swap is on for exactly one scan per cycle.
The toggle rung writes LeadB from two branches: Swap on and LeadB off, or Swap off and LeadB on. With Swap off it keeps LeadB as it is. With Swap on it flips it.
PumpA runs while LeadB is 0 and PumpB while it is 1.

Toggling without a one-shotIf Swap stays on, LeadB flips every scan and the pump choice is random.
Swapping while a pump runsSwap on the end of demand, as here, so a running pump is never switched over.