+1
Cat 6
As all have said, very versatile and as Ken says , very secure.
While you are doing it run as many as you can in the one conduit without overdoing it.
Leave a draw rope in it after every pull.
If you can afford it, run 32mm or 40mm or bigger (white) comms conduits.
Cables can be drawn thru 32mm so much easier later , but over 75m
I'd suggest an intermediate pit or access point!
You would be hard pressed to get something through 75m of 32mm conduit later.
Then run as many spare empty conduits as you can also!
I also have 4 core for security and 2 pr shielded for RS232 comms in
the same run.
I have RG59 coax for cameras also but that is now redundant as the
camera is an IP webcam.
Power and comms conduits can be in the same trench but must be 600mm
below the bare dirt.
Under concrete path I think it can be as shallow as 450mm but I must check that.
It's been years since I did pit n pipe and rules change.
I also have fibre between dome / house / shed for duplicating the controls remotely of my scope.
But that is all redundant now as LAN is just as
effective using ASCOM. Fibre is lightning proof but when your
outbuilding and house are on the same supply it removes that isolation anyway!
Steve