GE Low Voltage Lighting control system was ahead of its time

 In early 1960's General Electric released an advanced  low voltage lighting control system which used a series of   24 VAC  3 wire relays( middle picture )which was years ahead in its design . It allowed the controlling of all lights in the house from one master location or multiple locations which was a great security and energy saving  feature . The parts are still available as far as relays but some of the fancy low voltage switches are no longer available like the master control at top left .
Many electricians throw there hands up in the air when they run across these systems but they are actually very easy to trouble shoot

 if you understand them. While attending OVT Electrical training at South Vocational  we had several boards set up with these controls  which you could wire up several different scenarios.
The systems where expensive to install so you normally only ran across them in high end homes I have run across a dozen in 35 years in the field, but they where used in some commercial buildings as well. One of the largest installs ever done with this system was the now demolished Civic arena in Pittsburgh Pa.
This whole system had  no fancy switching electronics like today's systems  just simple relays. You will also find the name Bryant  on some switches as well which Licensed them thru GE.

At bottom left is a typical rocker low voltage switch you would find next to a standard wall switch you pushed one way light went on pushed other way light went off .

The only parts available are the simple rocker switches and relays very expensive to replace and repair. and only a hand full of us left that work on them.