I wanted to build a simple elevator that uses items and tripwire to transmit signals up and down over long distances. I noticed that the tripwires do not always activate. I tested a little bit around and found out that other small entities get affected too and do not always activate the tripwires or Pressure Plates.

I got around the issu by using trapdoor that only open if an Item is above inside the string.  

[Screenshot|https://cdn.discordapp.com/attachments/678684911149776906/678684990426316800/2020-02-16_20.09.12.png]