One of the responses below tries to demolish the idea of a vacuum train. Well I disagree. If you have a very long conduit without a draw-string to pull your your cables through there is a simple trick.
- Find a very long piece of string. Tie a number of very long pieces of string end-to-end until it exceeds the length of conduit.
- Get a tissue or paper napkin and scrunch it into a ball smaller than the diameter of the conduit. Don’t want it to get jammed!
- Recruit someone to hold the other end of the string or tie it off to something solid. Perhaps tie it to the end of the cable destined to go throught the conduit. No empty miles!
- Duct-tape a domestic vacuum cleaner nozzle to the far end of the conduit and start sucking. Point 3 is very important or your vacuum cleaner will eat all the string and you will have to start again.
I have done this domestically installing fibre but I learned about it from telco techs who do it daily over kilometres of conduit.
You don’t need a true vacuum — just a pressure differential and a bit of magnetic levitation to reduce friction. Vacuum trains! What will he think of next.