Total Newbie on a budget

[bitternboy]

That diagram shows the typical set up for using switches at the ends of travel to stop current flowing and letting the motor push it any further, sorry for being confusing :P

The ends with V+/- are the voltage you would be supplying from your ESC. The things labeled "NC" represent switches that are activated when the limit is reached, one for each end; NC stands for normally closed, so when it hits the end, they are opened.

The components represented by the arrow and line are diodes. Their function is to only let current flow in one direction.

The M in the circle is the motor driving the lin-ac.

Imagine the lifter is halfway up. Both switches are closed, so the diodes are redundant/bypassed and current can flow in either direction i.e. you can tell the ESC/relays to provide a voltage across the circuit in either direction and the motor can spin in either direction, raising it up or down.

Now the lifter hits the top of it's path, you don't want the motor to try and keep pushing because you'll break the mechanism or stall the motor. One of the switches is at the extreme however and is activated/opens. This means that if current wants to flow through the circuit it has to bypass the switch and flow through the diode instead of the switch. The diode won't let current flow in the direction that would result in the motor trying to push the lifter beyond its limit.

The other switch is still closed so it can still move back.

The same thing happens with the second switch and diode for the other limit.

Hope that's more helpful.

EDIT: Ah, got beaten to it :P