This has been posted on a few times before. I believe the delay I used was 1/2 second. the problem is that the Key piece doesn't shut the door after the second code, but waits several seconds before making the switch. This is true of the RS232 as well. One person has done it with the RTI remote and still has the occasional glitch. It's fairly reliable with an MX850/MRF300 combo (I wouldn't use a 250) but part of the problem is the control itself. Had they just given us complete discreets and shorten the delay before it switches then it would be 100%.