ISOFIX is an international standard for lower anchorages for child restraints. (That is the "bars" in the seat bite). LATCH is an acronym of sorts: Lower Anchorages and Tethers for CHildren used in the US that refers to both the lower anchor anchorages and the "top tether" which secures the child seat against rotation (forwards) in a crash. Most current generation European cars have ISOfix lower anchorages. The system introduced in North America through FMVSS 225 also includes top tethers (not required in Europe yet). The major aim of ISOFIX / LATCH is to reduce the risk of mis-installation of the child restraint.
Does your car have "top tether" attachments (they would be on the parcel shelf). From memory FMVSS 225 has a phased introduction which requires manufacturers to fit top tether anchorages for rear seats with a later introduction of a requirement for ISOFix type lower anchorages (the top tether can be used in combination with the conventional seatbelt type attachment).
Have a read of http://www.nhtsa.dot.gov/people/injury/childps/LATCH/ for more details.
I'm in Australia so I don't know which model years were fitted with what for the US/Canada market, but we've had top tethers since the '70s.

Mark

I've done a lot of research about carseats- we have a 98 S70 GLT and a 96 855R.

Neither has the LATCH system. I've never heard of the ISOFIX. My understanding of the LATCH system is that it is an attempt to avoid poorly installed carseats. The stats suggest as many as 80% of the carseats on the road today are improperly installed.

In the S70, I used a Britax Freeway. The tether bolt/hanger is installed in the trunk, under the rear deck, and the rear tether goes around the center headrest. I always use the center rear seat position, but we only have one child. The seat belt has a small switch on the back of the part on the belt that will allow the belt to remain tensioned with a car seat installation. It works fine, but I back it up with a locking clip supplied by the seat manufacturer anyway, as it will lose tension over time.

The 855 is a new (to me) car, and for that I bought a used (I know) Priori Cosi seat. I think it's a better product than the Britax, but it's not been tested in the US. It has, however, been tested in Europe, where the standards are higher, and include rear and side impact test data, unlike the US standards. The tether screws into the seatback.

Here is the most important part (my opinion) of a seat installation:

Make It Tight and Secure!

The best way to do this is to install the seat loosely according to the manufacturers installation instructions (READ THEM!) to place the car's belts in the proper places and buckle the seatbelts loosely. Then, have the heaviest member of your family place one knee in the seat where you childs butt will be, and kneel hard, pushing the seat down into the car's seat, all weight on the one knee. At the same time, tighten the car's belts. If done correctly, the seat will NOT move side to side without huge efforts. It really is strong and solid.

Oops- the kids waking up. Gotta run, hope I've helped!

p