Talkswitch 24-CA User Manual page 226

Depending on how the jack is wired, the phone can be plugged into Line 1,
Line 2, or both.
Single-line wiring
Dual-line wiring
Demarcation Point
This demarcation point shows two lines (four wires) wired as two loops.
2 1 4
For a single incoming phone line, all
phones in the building will usually be
wired using the RED and GREEN wires of
the phone cord. The other two wires,
BLACK and YELLOW, are not used.
The demarcation point connects the
incoming RED and GREEN pair to various
loops within the building. It is probable
that the building is also wired with a
BLACK and YELLOW pair, however these
are not connected to any wall jacks.
Two incoming phone lines are denoted in
pairs, usually the RED and GREEN are used
as Line 1, and the BLACK and YELLOW are
Line 2. All four wires are looped
throughout the building so that each jack
has access to Line 1 and Line 2. How each
jack is connected to the RED, GREEN,
BLACK, and YELLOW wires determines if it
is connected to Line 1, Line 2, or both.
The demarcation point is the point of
interconnection between the telephone
company facilities and your building.
Location: It is usually a box located inside
the building, within 15 feet of the
incoming phone wiring. In newer houses,
it may be located near the fuse box.
Wiring: The box will contain at least four
posts used to branch the incoming wiring
to the internal phone wiring. The RED
post should have all the RED wires
attached to it, the GREEN should have all
the GREEN wires attached etc.
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