Complex technology is anything whose capabilities are more important than their users' characteristics.
This category may include vehicles, systems, machinery or even buildings and similar structures. But do not think that every such thing needs to be represented mechanically in the game. It would be boring and tedious if we had to produce a sheet for every car out there.
Therefore before you write up a complex object into game terms, make sure it fits one of the guidelines below:
Its behavior depends on something other than the actions of a single character.
Maybe it has a crew, or maybe it is automated. In any case, it is not an
extension of a single character. A building security system with multiple
sensors, operators and guards is such a thing.
Its capabilities are far more important than the skill of its operator.
Probably it is optimized for a purpose, and that makes a bigger difference
against other non-optimized things, regardless of the operator skill.
A combat helicopter with all its weapons and avionics systems may be
a good example.
In any case, before starting to define a thing as complex tech, ask yourself this question: Does it matter for the story? If you are entering a corporate HQ in order to interview the CEO, the building's stats don't matter. If you intend to bomb the building, its stats still don't matter. If you intend to stage an assault on the building with multiple ground and air units, only then its stats begin to matter. If a tank is chasing you down the street, and you have a pistol, do not bother about the thickness of the tank's armor, it is thick enough. Run, you fool!
In other words, it only matters when it is a challenge for everyone involved.
Now that we have decided that it is worth our trouble, how do we model our complex thing? Well, just like we model a character; With skills(called capabilities), upgrades, aspects and stress tracks. The only difference is that we don't have a rigid template like we have for the characters. The number of characteristics a complex object has is solely based on your table's discretion. Only one aspect? OK. Eight upgrades? Good. No skills? Fine, it's your call.
In other words, skills for complex tech. Capabilities define the baseline for what this thing is good at. Used just like a skill roll, you add the capability's value to a 4dF roll, and compare it to either a static difficulty number or an opponent's roll tin order to determine your shifts.
Unlike skills, capabilities are almost always assumed to be self contained, that is, the thing has, by default, everything it needs to use its capability. A character would need a pistol in order to attack with his Firearms skill, but a tank is assumed to have an integral stabilized AT gun with SABOT rounds if it has Anti-armor:4 as a capability. Otherwise it wouldn't have that.
Capabilities take a number between 0-5, but most will be in the range 1-3. The number represents the relative advantage of the capability against other things of a similar function and scale. Do not compare the Sensors capabilities of a man-portable microwave field scanner and an AEGIS cruiser. They work on different scales and aren't comparable.
There isn't a normative list of capabilities but here are some samples that you can use. Experience has shown that stories become more interesting if you name capabilities after methods, opponents and environments rather than qualities like Power or Speed.
Mobility: Road, Off-road, Water, Underwater, Low altitude, High altitude
Offense: Anti-air, Anti-armor, Anti-personnel, EW, Anti-IC
Defense: Stealth, Evasion, Net-security, Security
Awareness: Sensors, Intelligence
Tech aspects and upgrades are quite the same as any other aspect and upgrade in the game. They define special story elements and rules respectively. Tech upgrades do not necessarily cause stress of any kind, but you may define them as sources of stress at the discretion of your table.
Stress tracks for complex things are again, quite similar to character stress tracks. Their base stress threshold is determined by the table.
Most things will at least have an Integrity track that represents their ability to keep on functioning. The thing will malfunction or break down if taken out on the Integrity track.
When it matters, vehicles may also have a Crew track. Taken out means bad things happen to people.
Complex things may have any other tracks that represent other fragile features. What they are, and what happens when they flunk is again your call.