Volta Reve 18A is a reversible brushless ESC. It is able to turn the motor in both directions and can fast change between these. Can be used for the so called "4D flying" where the model can hover prop down or fly backwards etc. In comparison to the variable pitch "4D" prop, this system is much simpler and crash resistant. Ideally you should prepare different flight conditions (if your Tx allows) so you can switch between normal mode of operation and 4D. Watch the video on this page to see how.
Calibration:
Fast start: switch on your transmitter and put the throttle stick to "max" position. Plug in the model battery. After some beeps, pull the stick to the middle. After some time you will hear another beeps and now you have 4D ESC: from mid throttle (on the stick) up, the plane works normally. From mid throttle down, it works in reverse.