I've been in the security business for a while, largely in industrial settings, and have a couple of things to pass on.
No conduit which contains line voltages can contain any low voltage wires. So, if you are running 110/220 ( or anything else ) power in a conduit, you can't pull in a 22/2 for your telephone, or an 18/4 for an intercom to the kitchen or your wife's sewing room. Now if you want to convert your telephone, internet or cable TV so it runs over fiber optic cable, you CAN put that ( FO ) in a conduit with power, because the FO won't carry electricity.
Generally in the security business, if a wire is used for current, meaning to operate a door lock, to report back the status of a door alarm contact, or signals from a "request to exit", etc, those functions use unshielded wire. If the wire carries data, for example from a card reader, it IS shielded. They do make some cable called "composite" which contains the conductors for both locks, contacts, etc., AND the data from a card reader, and usually the conductors are bundled by function. The bundles for devices aren't shielded, the one with data wire in it, is shielded.
Conduit is cheap, and considering the cost of it, if you are burying one for power between your house and a new garage, bury TWO, and put in only a pull string in the extra one. That way, no matter what you want to use the spare for later on, you can pull in the proper wire with the string. Even if you don't intend to ever run a low voltage circuit to your garage, in the event that your power circuit blows, you already have a conduit for a new circuit without having to do any excavation.
On string: put a string in your power conduit too, in case you want to add another circuit later on. In all of our industrial projects, we always wrote the specs to include a string in ALL conduits and also an extra conduit with a string in it.
I think wireless is overtaking the IP ( internet protocol ) world in many places, but if you want to run CAT5E or CAT6 for your garage computer, ( don't use CAT5 any more ) ( remember the 328' / 100 meters limit for CAT wire) put only "water blocked cable" in the conduit. As several members have said, water always finds a way into underground conduit, ( except maybe in Texas or Arizona ) and while the water won't harm most PVC or Teflon cable, it does effect the impedance of the wire and will cause problems with the data arriving in a form useful to the computer.
Lastly, when you buy the wire for your underground runs, also buy a roll of "cable trace" That is a tinfoil-like tape, generally red on one side, but made of aluminum foil. After putting a couple of inches of backfill over the conduit, lay a stretch if this over that fill, but before finishing with the rest of back fill. Run the ends of it to the foundation, then up to the surface. If you don't like the looks of it, you can cover the ends, but leave them where they will be easy to find when you need them.
First, if someone is digging, and IF the operator is watching where he is digging, he will see the red foil before he punches the bucket teeth through your conduit. ( HOPEFULLY ) But the biggest reason for the trace is so that years later, when you want to do some digging in the yard, but you don't remember where the conduit is, you will be able to find it. Just go to a rental store and rent a cable sniffer, a wire hound, or whatever they call them in your part of the country, and you will quickly and easily be able to locate your conduits.
Someone may argue that some of these points are not required by the NEC, but they all lead to a more professional job, and one that is less trouble prone as it ages. If you are planning to stay at that location for a long time, the last thing you want is trouble.
JBP
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