I have just been trying to figure out why they used low voltage inside interior lighting systems in the 60’s and 70’s ?
As far as I can tell, it was mostly put into upper higher priced homes…, so maybe it was just a type of fad at the time ?
Thinking back to that time, I believe it was because someone convinced folks that the installed cost would be less (less-expensive wire?) and/or that there were various control options (pathway lighting, group diming, etc.) that were difficult and expensive with conventional wiring.
The low voltage systems were popular for a while but they never caught on in a big way. The reason you mainly see them in higher priced homes is because they were an expensive luxury.
The idea behind them was to be able to have control panels located in key locations such as the master bedroom and the kitchen. The control panel made it possible to turn lights at any location off and on.
The systems were electro-mechanical so they could use much less wire than a conventional system. There were still a lot of wires so there was a big advantage to having small gauge wiring.
No real standards ever developed so the components from different manufacturers generally were no compatible with each other. The best systems are addressable. Addressable means that devices can be daisy-chained with a single cable. The older systems were not addressable.
They were not cost saving systems because the low voltage only controlled the system. They did not eliminate the need for most of the traditional power wiring. Also, the insulation on low voltage cables is usually a lower voltage rating than power distribution wiring so they had to be installed in separate conduits.