Belgium central office telephone wire color code, residential quad:
signal name BE-vvt BE-pet USOC info
A tip white* orange green 0 VDC primary pair
B ring blue* blue red -48 VDC
A2 tip green white black 0 VDC secondary pair
B2 ring violet gray yellow -48 VDC
*The polarity convention of white/blue changed in the 1990's.
USA: bell wire = yellow = usually connected to green
1. 1980's in-house wiring
Each socket has 5 holes, 4 contacts with screw terminals and 1 key.
There is one master socket with two extra screw terminals. The
in-house VVT cable connects all sockets in parallel. The wire color
code is:
key
O
white a O O s violet
blue b O O gnd green
c d
An external slave bell is connected over terminals a and s.
The incoming star quad was connected to the master socket as
follows:
the active primary pair : (-) to a, (+) to b,
the reserve secondary : (+) to c, (-) to d.
Screw terminals c and d are insulated placeholders. There is no
terminal for the key hole.
The telephone push button shorts a to gnd. In old installations
the drain wire of the incoming central office cable was connected
to the in-house gnd wire. Typically the wire was twined about the
conductor of the green wire in the screw terminal.
The b wire is switched to the in-house bell wire s by the master
telephone. When off-hook the bells are disabled since dialing pulses
would otherwise cause bells to tinkle.
The master socket contains a bell enable switch, b to s, shunted
by an RC circuit to guarantee low volume bell. The test circuit,
a to s, also gives old telephones some bell current.
Schematically RTT86RG044:
+--RC--+ anno 1988 test circuit 4.7 Kohm + 1 uF, or external bell.
a /s
/sw/ | switch closed if no plug in socket.
b/ | anno 1976-1985 shunt circuit: 4.7 Kohm/1W + 12 uF,
+-C--R-+ guarantees low volume bell.
Hence, unplugging the master enables the bells unconditionally.
Telephone internal bell connection:
old: b -- sw1 -- bell -- s, anno 1970 bells are in series,
new: b -- sw1 -- s, enable slave bell,
s -- sw2 -- bell -- DC block cap -- a, enable internal bell,
bells are in parallel.
When off-hook, sw1 disconnects s, and sw2 disconnects the internal
bell.
A new telephone can be made slave by unbridging b -- sw1 -- s.
Also, conversion for two wire operation can be done by rewiring
the plug: disconnect s for a master phone, or connect s to b for a
slave phone.
2. BE plug to rj11 socket adapters
BE equipment, at least Ascom's up to 2000, has bell wire switching.
If sold with a BE plug to rj14 socket adapter, the pinout of the
adapter is:
BE contact name gnd a b s RTT92RG093 BE plug to rj14 socket
wire color g r bl bk RTT93RG5906 rj14 socket BE socket
rj14 socket pin 2 3 4 5
usoc color bk r g y
signal name acc B A bell
polarity n/a - + =p4 pin 5 switched to 4 by equipment
This socket pinout and polarity matches USA practice. Using a 2 wire
flatcable gives 2 wire operation. Adapters are cascadable if using
straight through rj14 cable.
Answering and fax machines came with a BE plug to an rj25 socket
adapter, on the side, and a BE socket on top. The top socket was
disconnected when the equipment went off-hook. Older equipment used
a 6p6c rj25 with pinout at the adapter:
BE contact name b' gnd a b s a' BE top socket a' b' gnd s
wire color wh g r bl bk br BE plug to rj25 socket fax
rj25 socket pin 1 2 3 4 5 6
usoc color wh bk r g y bl
signal name A' acc B A bel B'
polarity =p4 n/a - + =p4 =p3 switched by equipment
Newer equipment used a 6p4c rj14 side socket as follows:
BE contact name a' a b b' BE top socket: a' b' gnd s
wire color g r bl bk
rj14 socket pin 2 3 4 5
usoc color bk r g y
signal name B' B A A'
polarity =p3 - + =p4 pin 2 and 5 switched by equipment
The gnd and s are wired through from plug to socket.
3. House wiring for answering machines and facsimile equipment
In larger houses telephone wiring typically consists of star wiring
to some sockets, followed by parallel extentions further on.
Recabling or rewiring is often infeasible due to the work required.
Converting such an installation for office with fax required
following steps:
0. remove the RC bell circuit and socket switch,
1. verify that all in-house cables are in parallel,
2. connect the CO line to the in-house first pair, however such that
the socket a is (+) and b is (-),
3. connect the fax with an rj14 adapter to a socket,
4. connect the house bell from gnd(+) to s(-),
5. rewire telephone plugs to use the secondary gnd/s pair,
5. near the fax leave a backup phone with plug wired to a/b.
Using a BE plug to rj14 adapter lets the fax switch the a/b pair to
the gnd/s pair.
When a dedicated fax number is subscribed to upgrading is
straightforward: swap the rj14 adapter for a 6p4c fax adapter, then
connect the fax circuit to the a/b pair, and the voice circuit to the
gnd/s pair.
4. 1990's dual circuit wiring
Since BE93RG5302 the internal socket switch is no longer present.
A socket thus is a 4 contact pass-through device which supports two
independent pairs. The new polarity convention is to connect (+)
to a and (-) to b. The in-house VVT wire color code to the socket
contacts, case top view, is:
key
O
white a+O O-s violet (b2)
blue b-O O+gnd green (a2)
The case size is W5 x H8 cm.
The active pair of the incoming star quad is connected to the left
a(+) and b(-) terminals. New BE plug to rj11 socket adapters are
wired taking the a/b polarity into account:
BE contact name s b a gnd
BE polarity - - + +
rj14 socket pin 2 3 4 5
usoc color bk r g y
rj14 signal name A2 B A B2
rj14 polarity + - + -
The polarity of the secondary pair is reversed, compared to rj14,
but allows for backward compatibility with (2.) by using a rollover
cable.
The secondary pair is typically used for ADSL. For DSL a low-pass
filter is required at the CO cable entry point. At that point the
incoming pair connects to the filter and to green/violet. The
filter output is plain old telephone service and connects to
white/blue.
The green/violet pair forms a circuit to the modem installation
point, without branches or further parallel extensions. At the modem
socket the two pairs may be split. A fax adapter gives the primary
at its rj14 socket, and requires the modem BE plug wired using the
secondary. A modem adapter gives the secondary at its rj11 socket
and the primary a/b on its top BE socket.
5. The NTP2007 and TF2007
The network termination point, NTP, is a socket installed at the
CO cable entry point. Its size is about 8 x 8 cm. Three pair screw
terminals connect to the 6 contacts of the socket. Schematically,
in top view with X a wire terminal:
a2--RC--b2 TEL green
10k + 470nF a2+X white
test circuit b2-X blue
dsl
IN black in O- tel DSL blue
orange a+X +O O+ O- b1-X (violet)
blue b-X -O O+ a1+X (green)
A double pole switch connects IN to TEL when no plug is inserted.
The in-house VVT green/violet can be used as a DSL circuit to the
modem location.
The telephony filter, TF, is a 6 pin plug with an rj11 dsl socket.
The a/b input signal is low pass filtered and relayed to the a2/b2
tel output. The plug's other outputs, the center column pins and the
rj11 socket, are connected straight through from the a/b input.
Inserting this plug in the NTP opens the switch and the filter thus
passes telephone service from IN to TEL. Also IN is connected
straight through to DSL and to the plug's own rj11 socket.
6. CO cable characteristics:
The primary pair runs to the left when facing the premesis from
the street. The secondary pair usually runs to the right.
O/B intro W/G
headend feed | swg 22 | headend loop
-<- TP1 --<----+ junction +---->-- TP1 --+ swg 20
-<- TP2 --<--------------------<-- TP2 --+ 0.52 mm^2
street bundle
RTT line characteristics
on-hook voltage 42..50 VDC
off-hook loop current max 80..84 mA (10 mA when no dialtone)
impedance 270 Ohm + (750 Ohm || 150 nF)
dailtone 440 Hz, -12 dBm, 0.2 Vrms
7. US rj11 4-wire color code residential
top
pin 1 2 3 4 5 6
rj14 male plug hook underneath b r g y
cable
signal name A2 B A B2
polarity + - + -
A/B = tip(+)/ring(-) = green/red black/yellow
CO marked pairs 1 2 3 4 5
tip/ring = white/blue white/orange white/green white/brown white/slate
Tip colors secondary White (W), Red (R), Black (BK), Yellow (Y), Violet (V)
Ring colors primary Blue (BL), Orange (O), Green (G), Brown (BR), Slate (S)
Keyboard rj11 plug (view at keyboard side)
top
pin 1 2 3 4 5 6
rj25 male plug hook underneath shield +5V GND res DAT CLK
reset is not connected cable