I have recently bought a winch up mast to gain greater height for my antennas, the electric winch lifts and lowers the inner section.
The 12v winch is designed for All Terrain Vehicles (ATV) and came from Winch-It complete with wireless remote control, in order to use the remote controls out of direct sight of the mast, I fitted proximity switches which detect when the mast is either fully raised or lowered, and then stop the winch.
The short YouTube video shows the type of switch used and its detection distance.
A more detailed mast installation and control blog is HERE.
Note – As demonstrated in the video, the orientation of the magnet is critical for correct operation, also the output from the switch is a signal voltage and a relay module must be used to avoid damaging the switch.