 The forward-reverse circuit uses a very specific type of starter. You're going to need a starter that has two coils, which will include a forward coil and a reverse coil. Now let's take a look at what the control schematic looks like. So here we have our basic forward-reverse control schematic. We have a forward coil and we have a reverse coil. The forward coil has some contacts associated with it. So we have a normally open contact that will close when this coil energizes and a normally closed contact that will open when this coil energizes. We also have a reverse coil, so that here is right there with the letter R and it will have two contacts associated with it as well. A normally closed contact that will open when it's energized and a normally open contact that will close when it's energized. Now you'll also notice that I have this dotted line linking the two forward and reverse. That is a mechanical interlock and its purpose is to make sure that the forward coil and the reverse coil do not pull in at the exact same time. If you do that, you end up with a dead short on your three-phase system and you end up with what I call cablazol flam, which means basically you're going to blow a fuse. So you're going to have a mechanical interlock, which is necessary, which is why it's a very specific type of starter. We also have, because we definitely don't want those two pulling in at the same time, is these sets of contacts, these normally closed contacts. These are called the electrical interlocks. And so what will happen is when forward is energized, this will open, which will not allow anybody if they try to press this button down to energize the reverse coil. And vice versa, if this coil is energized, then the R opens. And we'll talk about that and show you a little bit more in depth as we walk through how the circuit works. So here I push down the forward button. Current can flow through and it can energize F. So F becomes energized. And when F becomes energized, these normally open contacts become closed and these normally open, closed contacts become open. So what will happen now is current can also flow through this. This is my holding circuit because what will happen is I will let go of this button. It will bounce back up and this part of the circuit here will hold it in. So there we go. The button's up. F is still energized because of this contact, which holds it in as well. Now let's talk about down here. Let's say that somebody wants to come along and push this button because they're not paying attention. We don't want this coil to pull in, but you notice that with F energized, this contact here, which was normally closed, is now open. So if we press this button down, nothing can get through. So here we have the button pressed down. This was normally open. Current is still flowing through here, keeping F going. Current can also come down here, go across here, but then it is blocked by this set of contacts that are now open and R cannot energize. Now we can shut the whole system off by killing it with the stop button, which is a normally closed button. We push that down, that stops power from everything. So then F de-energizes and the circuit goes back to its normal state. Now to show you that the reverse is the same idea, current can flow down here, cannot go across there, cannot go across there, goes across, goes through the F normally closed contact, energizes R. R becomes energized, which means that the normally closed open contact here closes and holds in, as well as up here, R opens. As with the forward, when this button is up, this energizes still because we have the holding circuit engaged. Now let's just show if we press the F button that F will not engage. So again with R energized, if I go to push F down because I'm not paying attention, this locks me out. This normally open contact here, sorry this normally closed contact that is now open is open because this is energized. I cannot get any power through to my F, therefore I cannot have F and R energized at the same time. Now if something happened and R somehow closed or was the contacts were held closed for whatever reason, they welded shut and I've got this and that closed at the same time, this will prevent no matter what, if I have this go through, this tries to energize, this mechanical will hold it out. So what'll happen is like a little paddle, when this is energized it pushes on the paddle. So this one, even though it'll try to energize, it will be impossible for it to energize. So it's a redundant system to make sure that F and R do not energize at the same time. And then as before to stop the circuit, we just hit that stop button which is normally closed. It kills power to the whole circuit and everything goes back to its original state.