DIYbanter - View Single Post - Low-voltage house wiring from hell

From: indago

A remote low voltage switching system would be extremely desirable in the
case of long corridors in large buildings to control the corridor lighting
from several different places rather than using the usual 3-way and 4-way
lighting switching systems to reduce the voltage drop on the long runs of
lighting wiring.

It is also used for energy management. Computerized BMS systems (Building
Maintainence Systems) control the lighting levels based on occupancy and
ambient daylight.

In a residential setting, master stations of 16-24 zones allow one to actually
see which rooms are lit and which are not.

The OP is lucky that his system has one central location for the relays. This
arrangement defeats one of the acclaimed benefits of a LV system - saving wire.