This is an FMS 3 Second Landing Gear Door Sequencer, for use with the FMS 1400mm sized Zero, T-28, P-38, B-25, Corsair and F6F. All these airplanes should use the PZ retracts which function in less than 3 seconds - please ensure this before purchasing this item.
This sequencer is a timed system used to control the landing gear with RC airplanes to provide scale and realistic landing door sequence. The latency effect is 3 seconds. It means that the wheel door will close in 3 seconds. Therefore, the sequencer needs corresponding retracts to operate in less than 3 seconds, or the door will close before the landing gear returns back in the tank.