UPDATE: I got a 5 pin male to 3 pin male connector and connected the machines using the "Output to next unit" on the master fogger to the "remote control input" of the slave fogger. Unfortunately they don't fog at the same time as I was hoping for. With the timer on or continuous fog on, only the slave fogger fogs, if I hit the Manual button on the remote, only the master fogger fogs. Any ideas??? I went ahead and purchased a 3 pin male to 3 pin male adapter as well and I'm going to try the other suggested idea of connecting the foggers by using both " Output to next Unit" jacks and see if that does it. If that doesn't work, I guess I have no idea what VEI meant by being able to run these machines in series.