Sequencer is a time system used to control RC airplane door and landing gear working in the proper order. Different sequencer has different effect. We have three different sequencers now. They are for different airplanes.
FMS Sequencer-6 sec
The latency effect is 6 sec. It means that the wheel door would close in 6 sec. Therefore, the sequencer needs corresponding el retract which must play in less than 6 sec, or the wheel door shall close before landing gear back in the tank. 
