It looks like you are looking at a direct wire system not low voltage. Yes, such lights exist - xenon, halogen, micro fluorescent and led.

Whether you have one or two switches depends on your envisaged use pattern. With home automation, two switches can be made to function as one when necessary.

Having said that, it is more logical to have the Ucl on one circuit so that it can be turned on/ off or dimmed uniformly.
The led Ucl DIY thread primarily concentrated on a specific make of low voltage light bar which is still being sold under different brands and vendors.

the layout principles still apply.

The upfront cost for led is typically higher than fluorescent, but there are factors that could make it more attractive - ability to dim, smaller profile, longevity.

I would recommend making mock up layouts with various options.

David -- I'm sorry for the delay in my response -- I thought I had posted earlier but I must have forgotten to send what I wrote after viewing it. .... thank you so much for the generosity of your time and shared expertise. As it happens it's so hard for me to figure out questions to pose coming from so far away understanding-wise.

I'm actually a little confused by your very first comment. I'd like to try to think through it and would appreciate someone correcting my reasoning if you're willing:

Isn't the opposite of low voltage not-low voltage? That is, normal voltage? So would normal voltage (that would be 110V, right?) be a synonym for direct wire system? Thus you can't have a direct-wired low voltage system?

Please forgive me for such dim understanding ... is this right? Electricity comes to the pole outside of the house at some high voltage. A transformer at the pole steps it down to 240V and then somewhere, maybe the electrical box, it gets split to 110V which is what is used to run all the lamps in the house, basically everything but your ovens. So that's "wired" and that's 'normal' voltage. Then 'low' voltage would have to be further stepped down -- that's what those transformer boxes everyone talks about sticking in their cabinets or in the basement do, right? They must be like the big cylinder out on the pole stepping down electricity from the high tension wires, they must step electricity down from 110V to something lower to run the LED lights....

Am I understanding that right please? Because otherwise I can't fathom this statement: "you are looking at a direct wire system not low voltage".

So am I right about this: I read somewhere long ago that those little transformer boxes which are always hot, are always on - that's why they're hot. So they're always on, always drawing current, always setting up electrical fields inside your house, right?

...except now I'm thinking ... these things would always be on if you *plugged them into a plug and then switched them on/off*. So ... if I had one of those switched lamps with a transformer plugged into a wall *it* would always be drawing current through the lamp whether on or off because there was no switch to the outlet. However, if you plugged the lamp into a switched outlet it could turn off the transformer box.

Is this right? Because if so then by analogy, the transformers for UCL LEDs could actually be switched and therefore off....

Please if you wouldn't mind following through with this electricity primer, would someone mind telling me if I'm getting this right? I'm asking because this is the reasoning behind my thinking I don't want transformers -- I don't want those things "on" all the time.

When folks talk about direct wire, it means standard voltage and alternating current.

For the low voltage lighting systems from environmentallights/ nora lighting/ .../photonier use direct current at 24V. Others use direct current at 12V.

The "transformer" that is connected to the lights is really a power supply with the necessary step down transformer. It is just like a laptop power supply.

The power supply ("transformer") is connected to a switch on the household AC circuitry which can be turned on/ off or dimmed.

House electrical supply
When power is generated remotely at a power plant, the voltage output is in 1000's of volts (kV) and the electricity is in the form of alternating current. The power is fed into transmission lines (High tension lines) and transmitted to places where it will be used. Nearer your home, there is a station that steps down the voltage to ~ 277V which is distributed to the neighborhood (typically on wires strung on poles).
The transformer on the pole outside the house steps the voltage down from approx 277V to about 110 - 120V which goes into your panel. The electricity coming into the house is AC (Alternating current).

Most electronic devices in the house require DC power at typically lower voltages, hence the need for a power supply.

Forgot to include a link to a more detailed description.

Here is a link that might be useful: Electrical power distribution

Thank you, David. This is all really helpful, a great clarification. It seems the polarity (if that's the right word distinguishing direct from alternating current) is a huge part of what this is all about then.

Is it true then that those transformer boxes people use for UCL LEDs get hot and are therefore on all the time? Or might they be wired so that the on-off UCL switch actually cut power to the boxes themselves?

TIA.

You would wire the power supply to a switch so that it is turned on only when needed. That was covered in the led ucl DIY thread.