[Roger 1]

thats interesting.  i do not have any slide pins on the bottom on either of my slides.  i see no benefit of having pins on the bottom since the hydraulic rams are there sucking it in.  

are you sure there are some on the bottom?

they used two different systems to engage the pins for sensors.  mine has round rare earth magnets about the size of a nickel superglued to the top of the slide adjacent to the slide pin hole.  the sensor on the slide itself is on the wall above the slide and can be adjusted up and down a little.  if the magnet and the sensor dont have good alignment, it will not trigger the pins to come down.  as the slide/coach ages and sags or moves, the magnets will need to be taken off and reglued on.  i just did mine last year to make it consistently trigger the pins.  even then sometimes i have to hold my head at the right angle to get them to come in....ha

the other system has microswitches somewhere.  

tom My slide has a scissor mechanism that pulls the slide in and pushes it out one on each side of the slide. My magnets are on the inside of the slide when I put a washer next to the holes where the pin goes in the washer sticks. I have 3 boxs up in the left front bay that have lights that tell me when the slides are in or out and if the pins are locked or open . Just not sure how I would get to the bottom locks top was easy . My other 2 slides only have 2 pins go figure!