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The Legion of Doom!
Presents:
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LOD Reference Guide Vol. I
Outside Loop Distribution Plant
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Written 12/86 Phucked
Revision III Agent
04
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INTRODUCTION / OUTLINE
----------------------
Basically, the outside local loop distribution plant consists of all
of the facilities necessary to distribute telephone service from the central
office (CO) out to the subscribers. These facilities include all wire, cable,
and terminal points along the distribution path. In this article, we shall
follow this path from the CO to the subscriber, examining in depth each major
point along the route and how it is used. This is especially useful for
checking if any 'unauthorized equipment' is attached to your line, which would
not be attached at the Central Office. I suppose this article can also be
interpreted to allow someone to do just the opposite of its intended purpose...
Note that this article is intended as a reference guide for use by
persons familiar with the basics of either LMOS/MLT or the operation of the
ARSB/CRAS (or hopefully both), because several references will be made to
information pertaining to the above systems/bureaus. I have no manuals on this
topic, all information has been obtained through practical experience and
social engineering.
********************
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Serving Area Concepts (SAC) plan
--------------------------------
In order to standardize the way loop distribution plants are set up in
the Bell System of the U.S. (and to prevent chaos), a reference standard design
was created. For urban and suburban areas, this plan was called the Serving
Area Concepts (SAC) plan. Basically, in the SAC plan, each city is divided
into one or more Wire Centers (WC) which are each handled by a local central
office switch. A typical WC will handle 41,000 subscriber lines. Each WC is
divided into about 10 or so Serving Areas (depending on the size and population
of the city), with an average size of 12 square miles each (compare this to the
RAND (Rural Area Network Design) plan where often a rural Serving Area may
cover 130 square miles with only a fraction of the number of lines). Each
Serving Area may handle around 500-1000 lines or more for maybe 200-400 hous-
ing units (typically a tract of homes).
From the CO, a feeder group goes out to each Serving Area. This con-
sists of cable(s) which contain the wire pairs for each line in the SA, and
it is almost always underground (unless it is physically impossible). These
feeder cables surface at a point called the Serving Area Interface (SAI) in a
pedestal cabinet (or "box"). From the SAI, the pairs (or individual phone
lines) are crossed over into one or several distribution cables which handle
different sections of the SA (ie. certain streets). These distribution cables
are either of the aerial or underground type. The modern trend is to use
buried distribution cables all the way to the subscriber premises, but there
are still a very large number of existing loop plants using aerial distribu-
tion cables (which we will concentrate mainly upon in this article). These
distribution cables are then split up into residence aerial drop wires (one
per phone line) at a pole closure (in aerial plant), or at a cable pair to
service wire cross box (in buried plant). The cable pairs then end up at the
station protector at the customer's premises, where they are spliced into the
premise "inside wire" (IW) which services each phone in the customer's premi-
ses (and is also the customer's responsibility).
Although this is the "standard" design, it is by no means the only
one! Every telco makes it's own modifications to this standard, depending
on the geographic area or age of the network, so it's good to keep your eyes
and your mind open.
********************
At this point, we will detail each point along the Loop Distribution Plant.
-----------------------------
Cable Facility F1 - CO Feeder
-----------------------------
The F1 cable is the feeder cable which originates at the Main Distribu-
tion Frame (MDF) and cable vault at the local CO and terminates at the SAI.
This cable can contain from 600 to over 2000 pairs, and often more than one
physical F1 cable is needed to service a single Serving Area (at an SAI).
The F1 is almost always located underground, because the size, weight, and
number of feeders leaving the CO makes it impossible to put them on normal
telephone poles. Since is is also impractical to use one single piece of
cable, the F1 usually consists of several pieces of large, pressurized or
armored cable spliced together underground (this will be covered later) into
a single cable.
Cable Numbering
---------------
In order to make locating cables and pairs easier (or possible, for
that matter), all of the cables in the loop distribution plant are numbered,
and these numbers are stored in databases such as LMOS at the ARSB or other
records at the LAC (Loop Assignment Center) or maintenance center. When trying
to locate someone's cable pair, it helps a great deal to know these numbers
(although it can be done without them with experience and careful observa-
tion). Probably the most common place to find these numbers is on a BOR,
in the "Cable & Assignment Data" block. The F1 is usually assigned a number
from 00 to 99 (although 000-999 is sometimes used in large offices). Cable
>pair< numbering is different however, especially in older offices; typical F1
pair numbers range from 0000 to 9999. Keep in mind that the pair number is not
concrete -- it is merely nominal, it can change, and it doesn't necessarily
have any special meaning (in some well organized offices, however, the cables
and pairs may be arranged in a certain way where you can determine what area
it serves by its number (such as in my area...heh heh); in any case, it's up
to you to figure out your area's layout). Anyway, the cable-pair number is
usually written in a format such as 02-1495, where 02 is the cable and 1495 is
the pair (incidentally, since this is the CO Feeder cable pair that is connect-
ed to the MDF, it is the one that will be listed in COSMOS).
F1 Access Points
----------------
Although the F1 is run underground, there is really not a standard
access point down there where a certain pair in a cable can be singled out
and accessed (as will be explained next). There is, however, a point above
ground where all the pairs in the F1 can be accessed -- this point is known
as the Serving Area Interface (SAI), and it will be detailed later. In LMOS
or other assignment records, the address of the SAI will be listed as the
TErminal Address (TEA) for the F1 cable handling a certain pair in question;
therefore, it is where facility F1 stops.
-----------------
Underground Plant
-----------------
The term "Underground Plant" refers to any facilities located below
the surface of the earth; this includes truly "buried" cables, which are
located 6-or-so feet underground surrounded basically by a conduit and dirt,
as well as cables placed in underground cement tunnels along with other
"below-ground" equipment (such as seen in most urban areas). Whereas the
first type is really impossible to access (unless, of course, you want
to dig for a day or so and then hack into an armored, jelly-filled PIC cable--
then you should take a bit of advice from our resident Icky-PIC "Goo" advisor,
The Marauder), the latter type can be accessed through manholes which lead to
the underground tunnel.
Manholes
--------
Bell System manholes are usually found along a main street or area
where a feeder cable group passes through. Using an underground cable
location map is the best method for locating cable paths and manhole appear-
ances, although it may not always be available. These maps can be acquired
from the Underground Service Alert (USA) (at 800-422-4133), but often a
"cable locator" will be dispatched instead (usually he will just mark off
how far down or where you can dig without hitting a cable), so this is not
a very practical method. Of course, you can always follow the warning signs
on telephone poles ("call before you dig", etc) and the spans between SAI
bridging heads until you find a manhole. The F1 for the SAI nearest the
manhole should be found down there along with others en route to the areas
they serve.
There are several types of manhole covers, both round and rectangular.
The rectangular ones are sometimes just hinged metal plates covering an under-
ground terminal or cable closure, and these are easily opened by one person.
A non-hinged one may require two people. Round manhole covers (which, by the
way, are round so that a lineman can't accidentally drop the cover down the
hole) are basically all the same, except for the types known as "C" and "D"
type manhole covers which utilize locking bolts (these can be removed using a
standard crescent or hex socket wrench). These covers are the same as the
standard "B","A", and "SA" type covers once the bolts are removed. The best
way to open a cover is to use a manhole cover lifter (ie. Defiance Corp. PTS-
49 or B-type Manhole cover lifter), although an ordinary 3/4 - 1 inch crow-
bar (hook-side) can be used. Put the tool into one of the rim slots and
press down on the bar until the hook is pressing up against the cover flange.
Then push or lift the cover a few inches up and slide it off the hole. You
can use a bent sprinkler turn-off wrench on the other side to lift up if there
are two of you. You should have no problem with two people, although it can
be done alone provided you are strong enough.
Once inside, check around for any test equipment or papers which may
have been left inside. Basically, there is really no pair access down there,
as it is mainly a place through which the protected feeder cables are run
and spliced together. These splice points are usually sealed in pressurized
air and water-proof closures which protect the open splices from corrosion and
ultra-violent rodent attack. If for some reason you happen to find an open
splice case or a cable with it's armor and sheath removed, then it may be poss-
ible (although not easy) to match color codes (see chart) and find a certain
pair. You would have to strip the wire near the splice, though, and this is
not recommended. Don't get the bright idea to pry open, or (worse yet) blow
open a splice case, as they are often pressurized (see "manhole dangers"), and
the telco will frown on your actions sooner or later. Anyway, the feeder cab-
les generally are labelled at a point near the manhole, so it is easy to find
and follow any certain cable. Because of this, the manhole access points in
your neighborhood are good places to examine (and even sketch or map) the
cable distribution plant in your area. This could be interesting, especially
if you find a lot of recently installed groups or special service cables, etc.
There could even be several types of apparatus cases containing either analog
or digital carrier equipment (ie. T1 digital or O,L,or N analog), pair gain
systems, repeaters, equalizers, or loading coils (which help compensate for
shunt losses caused by the parasitic capacitance between pairs in pressurized
cable). A typical underground apparatus facility is the BERT (Below ground
Electronics Remote Terminal). However, it's unlikely that you will find any
of this special equipment down there (other than loading coils, which look like
metal cylinders) unless you are in a very rural or specialized area, or you
happen to be in a manhole serving an inter-office trunk span (smile here).
Manhole Dangers
---------------
One must use good sense when entering a manhole, however, especially
if you don't have the right equipment. First, you could drop the cover on
your foot, or get a crowbar or bent sprinkler tool (the WORST) in the groin.
Secondly, you must take precautions if you stay down long, because the atmos-
phere in the hole will become oxygen depleted in a matter of minutes and there
may be suffocating or otherwise dangerous gases in the manhole. Third, if
you tamper with nitrogen-pressurized cables or closures, a depressurization
alarm signal may be set off at the maintenance center, and technicians could
be sent out while you are still in the hole. It is also known that expensive
electronic equipment mounted below-ground (ie. SLC remote terminals) may
be equipped with tamper alarms, and they are securely locked as well.
*************************
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Serving Area Interface - SAI
----------------------------
The Serving Area Interface (SAI) is basically the point on the loop
distribution path where the F1 feeder cable is cross-connected over into one
or more F2 aerial (or buried) distribution cable. This terminal can be pole,
pad, or pedestal mounted - however, for this article, we will concentrate on
the pedestal mounted cabinet as it is by far the most common (the other forms
are functionally similar, anyway). These things are seen all over -- the
4-foot high gray-green "boxes". There are several names for this terminal--
technically it is called the SAI or FDI (Feeder Distribution Interface), but
it is usually called a Bridging Head, Pedestal, B-Box (lineman term), or just
plain "Box." The standard cabinet is the Western Electric 40-Type cabinet, and
it comes in several sizes, depending on the amount of cable pairs in the
Serving Area. The size and style of the cabinet is usually stenciled or marked
on the cement pedestal at the base of the cabinet. (ie. S-40-E = 40 type, E
size, SAI cabinet). These cabinets can handle anything from 400 (A size- 200
feeder in, 200 distribution out - 43"H x15"W x12"D) to 1800 (E size - 900 in,
900 out - 54"H x 40"W x12"D), with some newer size F, H, and some 3M series-
4200 cabinets handling up to 3600 pairs at one site! Also note that 40-type
(or look-alike) cabinets are not exclusively for use as a SAI, especially in
areas using a buried F2 distribution plant. Note that all Bell System (Western
Electric) cabinets, cross-boxes, etc. which are pedestal mounted are painted a
standard grey-green (Technically, they are painted per Munsell Color Code
Standard, EIA RS-359. This color is supposed to be the least obtrusive and
most pleasing to the eye). This also helps to distinguish Telco boxes from
sprinkler and signal control boxes. Also note that there are still a large
number of older loop plants in the Bell System, and the terminal boxes may
differ (ie. nut-bolt type binding posts, panel-removal type cabinets, etc.)
in appearance, but the are all functionally similar.
To open a 40-type or other common cabinet, one must use a 7/16" hex
wrench (also called a "can-" or "216-" tool). Place the wrench on the bolt
and turn it 1/8 of a turn clockwise (you should hear a spring release inside).
Holding the bolt, turn the handle all the way to the right and pull the door
outward. If you happen to see a locked cabinet pried open by a crowbar placed
in the slot above the right door, you should report it to the telco AT ONCE!
On the inside of the door, there should be a circular attachment with a "D"-
type test cord on it which makes accessing pairs with a test set easier (if
you dont have a test set, I will describe how to make a basic one later in
this article). You should hook the alligator clips on your test set to the
two bolts on the attachment, and then use the specialized cord to hook up to
binding posts on the panel (it is specially designed to do so, whereas alliga-
tor clips aren't). There are usually also spare decals and 2 reels of #22
solid "F" cross-connect wire stored somewhere in the cabinet, either on the
doors in a box (along with a "788N1" tool for seating and trimming jumper
wires) or mounted in the splice chamber (described in the next section).
Locating Pairs and Cross-Connects
---------------------------------
Basically, the SAI cabinet contains several terminal block panels
(size A=1 panel, size C+D (800+1200 pairs, respectively)=2 panels, size E=
3 panels) of either 76-type screw binding posts (the most common) or more
modern 108-type "quick-connect" connectors. These panels are divided up
into 6 blocks of 100 cable pairs (2 screws = 1 binding post, per cable pair)
each, with block 1-100 on the top and 501-600 on the bottom. In a 2-panel
cabinet, the left panel typically contains the pairs from the F1 (feeder)
cable, and the right panel contains the F2 distribution cable pairs. This
is accomplished by either a harness or cable stub whose pairs are internally
connected to the binding posts on a panel. The harness or stub is then
spliced, usually with "710" splicing connector modules, to the respective
F1 or F2 cable. In the case of the harness, this splice is located in the
back of the cabinet, in the splicing chamber, which can be accessed by
rotating the notched circular latch on the top of the terminal block assembly
and letting the panel fall forward. Often the splices are covered with plas-
tic bags. Note the color code of the pairs; if you can locate the pair you
want, this is an excellent location to covertly access it, because this area
is rarely seen during normal use of the cabinet (it is usually only opened
during a cable cutover or "throw", in which a whole section of feeder or dist-
ribution cable is replaced at one time). In the case of cable stub, the
splicing is usually done underground at a closure, because the raw-ended cable
extends 20 to 100 feet from the cabinet; in this case, there won't be a splic-
ing chamber. This type is often used for aerial pole-mounted SAI's. Also
note that in an F-size cabinet, you have to remove the whole back panel in
order to access the splice chamber. Anyway, the pairs from the feeder panel
are cross-connected with wire jumpers over to the binding posts on the dist-
ribution panel; in this way, the two cables are connected.
There are several ways to locate a pair in an SAI. First, and best,
if you have assignment data from LMOS or equivalent, there should be an F1
Binding Post (BP) number listed along side the cable numbers. This number is
usually a 3 digit number, 001-999, and it will correspond to a binding post
pair in one of the hundred-blocks on the feeder panel side. The first digit
of the BP is the block, and the other digits represent the pair in that block.
Example-
Terminal Panel
(Green) (Blue) F1 pairs --F1----F2---
-- F1 Feeder --------- F2 Dist.---- ==>001-100 ! *** XXX !
F1 BINDING POST ! XXXXXXXXXX XXXXXXXXXX ! ! 101-200 ! XXX XXX !
# 025 ! XXXXXXXXXX SAI XXXXXXXXXX ! ! 201-300 ! XXX XXX !
! ! XXXXXXXXXX XXXXXXXXXX ! ! 301-400 ! XXX XXX !
------------------^ ! 401-500 ! XXX XXX !
(^^ close up view of first 3 of 10 binding post ! 501-600 ! XXX XXX !
rows of the first hundred block (marked ***)----! !-----------!
F1 BP # 025 : 0 = first 100-block, 2 = pass over 2 full rows (go
to 3rd row down), 5 = 5 pairs from left.
The color of the pair label is important, also -- feeder pairs are
always marked with GREEN labels. Secondly, if you don't have a binding post
number, there may be a log or other chart posted on one of the doors of the
cabinet showing the cable pairs and their corresponding binding posts (or the
posts may in some cases be arranged or labelled in a way such that the cable
pair number could be derived). Thirdly, as a last resort, you could connect a
test set to each pair in the terminal, and dial your area's ANI number (This
"ANI" number is usually a multi-digit test code which, when dialled responds
with a voice announcement of the Directory Number (DN) for the line you are
dialling from). This would have to be repeated until you happen to hook up to
the line you are looking for (it's time consuming, but it works). Some sample
ANI numbers are-
213 NPA - Dial 1223 213 NPA (GTE) - Dial 114
408 NPA - Dial 760 914 NPA - Dial 990
These numbers will vary from area to area, and some areas may not have
such a service (in this case, you may have to dial a TSPS operator and have her
read off the number on her ANI panel -- in some areas, you may have to say a
code word or phrase in order for her to give you the number). In any case,
it would be a good idea to ask a lineman or testboard employee for the proce-
dure to use in your area to get ANI, because it's very useful and you'll need
it sooner or later.
Anyway, once an F1 BP is found, the cross-connect wire can be traced
over to the distribution panel, and in this way, the F2 pair can be found.
These F2 distribution pairs are always marked with BLUE labels. Note also
that the binding post number of the cross-connected F2 pair is not recorded
in LMOS (the F2 BP is NOT in the SAI, so don't confuse an F2 BP number with a
BP in the SAI); however, when the cables are first installed, the feeder pairs
and distribution pairs are in sequence -- this makes it easy to visually ass-
ume where the F2 pair is. This order can be upset when cable pairs are added
or changed, however, so it can't always be relied upon to produce valid F2
cable pair numbers (also, there may be two distribution cables, with the
low-numbered pairs on the bottom and the high-numbered pairs on the top! -- It
all depends on how the local telco sets things up).
Floaters / Multiples
--------------------
All of the pairs in a feeder cable are rarely used simultaneously;
this would be impractical, because if one of the pairs was discovered to
be faulty, or if a subscriber wanted another line, a whole new feeder cable
would have to be added. To solve this, extra facilities are left in the
loop plant as a provision for expansion. For example; on the feeder panel,
all of the binding posts may be connected to F1 cable pairs, but not all of
them may be crossed over to distribution pairs. These spare pairs are not
connected to the switch, so they won't "have dial tone", but they are numbered.
Since these lines aren't assigned, they wont be found in LMOS, but they will
definitely be listed in LAC records. These records are the Dedicated Plant
Assignment Cards (DPAC) / Line Cards and the Exchange Cable Conductor Records
(ECCR), or even computerized databases (ie. MODE). If the numbers can be found
(or even noted, if the numbers on the binding posts at the SAI correspond with
feeder cable pair numbers) then the lines can be activated via a COSMOS service
order. This is aided even further by the fact that since F1's usually last
longer than F2 facilities, there are often more spare provisional F2 facili-
ties in the loop plant (ie. 100 feeders in, 300 F2 out (200 aren't cross-
connected to F1's)). So there is a good chance that you will find one that is
distributed to your area. Other spare facilities include "floaters", which
are like spare feeder pairs, except they are ACTIVE lines. Often, a telco will
extend whole feeder groups to more than one SAI in provision for future expan-
sion, including active cable pairs. If you find a working pair on a feeder
panel which is not cross-connected to a distribution pair, that pair is a
floater. This is by far the best way to covertly access a certain pair,
because most linemen will probably not be aware of the pair's presence (it
looks unused on the surface). Beware! If you think you can hook up to
someone's floater and get free service, you're probably wrong (so many other
people have been wrong, in fact, that Pacific Bell has a special "Form K-33"
to report this type of fraud), because the telco is more aware of this than
you may think. Obviously any toll call you make will show up on the bill for
that line. A do-it-yourself spare pair activation can avoid this problem, if
done correctly.
--------------------------------
Cable Facility F2 - Distribution
--------------------------------
The F2 distribution cable is the cable which originates from the F1
feeder in the SAI and distributes individual cable pairs to each subscriber.
This cable can be one of two types: aerial or buried. The most common is the
aerial distribution cable, although buried cable is the modern trend. In the
case of aerial F2, the cable or cables leave the SAI underground, and at the
first telephone pole on the distribution span, the cable is routed up the pole.
It then is suspended on the span, such as down a street, and at each group of
houses there is a terminal on the span. This terminal is the aerial drop split-
ter, and it's purpose is to break off several pairs from the distribution cable
in order to distribute them (in the form of aerial drop wires) to each house or
premise. The location or address of the premise nearest this aerial drop
splitter is the TErminal Address of the F2 serving a certain pair (each group
of pairs in the F2 will have it's own terminal address, unlike the one address
for the F1 terminal (SAI)). The F2 cable is always the lowest cable on the
telephone pole, and it is usually a great deal larger than the electric power
distribution cables above it. Often more than one F2 can be seen on a single
pole span. In this case, the top F2 will usually be the one which is being
distributed to the subscribers on that street, and the lower (and most often
larger) cables are other F2's coming from an SAI and going to the streets
which they service: These cables consist of multiple spliced spans, and they
will not have any drop wires coming off them (they are marked every few poles
or so at a splicing point called a "bullet closure" which is fully enclosed
and can be quite large (ie. 6" dia, 20" long) as compared to the normal drop
splitters (ie. or similar 4"w x 5"h x 12"l) -- these closures are clamp press-
urized and are not meant to be opened unless the cable is being replaced or
splicing work is being done. They are not shandard cable/pair access points).
Buried F2 plant is similar to aerial, except that the cable is not
visible because it is underground. Instead of going to a pole from the SAI,
the cable continues underground. The drop wires are also underground, and the
method of breaking them from the distribution cable is similar to that of the
aerial drop splitter, except it is a small pedestal or box located on the
ground near the houses it serves. This address closest to this pedestal is
the TEA for the F2.
F2 Cable Numbering
------------------
The F2 distribution cable is usually given a 4 or 5 digit number,
depending on the office. The first 2 or 3 digits should be the number of
the F1 that the F2 was branched off of, and the last 2 or 3 digits identify
the distribution cable. Example-
F1 Cable F2 Cable
25 2531
This F2 cable came from feeder #25^^
The cable >pair< numbers may be set in a similar way, with the last 3
or 4 digits identifying the pair, and the first digit (usually a 1) identifying
the pair as a feeder or a distribution pair. Example -
F1 Cable Pair F2 Cable Pair
25 1748 2531 748
^--signifies F1 (feeder) cable pair
Generally, the F1 cable pairs are numbered higher than the F2 cable
pairs, due to the fact that a feeder cable may contain several distribution
cables' worth of cable pairs. Note once again that all of this numbering
plan is the STANDARD, and it may be far from real life! As soon as one dist-
ribution pair is replaced, crossed over to another feeder pair, or taken from
service, the set order is interrupted. In real life, it is most always nece-
ssary to get both F1 and F2 cable assignment data.
********************
--------------------------------------------
Facilities F3-F5, Rural Area Interface (RAI)
--------------------------------------------
Although cable facilities F3, F4, and F5 may be specified in any loop
plant, they are rarely seen anywhere except in rural areas under the RAND
plan (Rural Area Network Design). Basically, plants using these extra
facilities are similar to F1/F2 plants, except there are extra cable spans
and/or terminals in the path. When locating cables, the highest numbered
facility will be at the end of the path, terminating near the subscriber's end
(like a "normal" F2), and the lowest numbered facility will be the feeder from
the CO (like a "normal" F1). The extra spans will be somewhere in between,
like an intermediate feeder or extra distribution cable with separate cable
access terminals. One such facility is the Rural Area Interface (RAI), which
can be used in a "feeder-in, feeder-out" arrangement. This is usually seen on
cable routes of 50 pairs or greater, with a length of longer than 30 kft
(about 6 miles). In this case, there will be two terminal cabinets in the
feeder path, labelled RAI-A and RAI-B. The RAI-A is special because it has a
two-part terminal block: the top has switching panels with 108-type connectors
which cross-connect feeder-in and feeder-out pairs using jumper plugs, and the
bottom has standard 76-type binding posts which cross-connect feeders to
distribution cables for subscribers in the local area of the RAI-A. The jumper
plugs can only be connected in one way to the switching panels, so random
cross-connection of feeder-in/feeder-out pairs is prevented. In this way, the
cable and pair numbers stay the same as if the feeder cable was uninterrupted.
This is used a lot in rural areas; it allows part of a feeder group to be split
off at the RAI-A like a distribution cable near a town along the route, and
the rest of the feeder group continues on to a town further away, to the RAI-B
where it is terminated as in a "normal" SAI. In order to access a pair, just
use the last RAI in the span (whichever it is) and treat it just like an SAI.
If the pair terminates at RAI-B, you can also access it at RAI-A! (if you
can locate the pair using color code, BP number, or (ughh) ANI, there should
be test terminals on top of the jumper plugs connecting the 108's on the
switching panel where you can hook your test set -- you can't hook onto a raw
108 connector very easily). Anyway, the RAI terminal is usually a ground
pedestal with a cabinet such as a 40-type, but it can be aerial mounted on a
pole (hard to access).
Pair-Gain, Carried Derived Feeder
---------------------------------
Another common facility in rural areas (and in cities or suburbs, es-
pecially near large housing complexes, etc.) is the pair-gain system. It is
basically a system which consists of a digital link which is distributed,
almost like a normal cable pair, out to a terminal cabinet called a Remote
Terminal (RT) which contains equipment which demultiplexes the digital line
into many "normal" metallic analog telephone lines which go to each subscriber
in the area. Because the digital line can transmit the audio from several
separate lines and multiplex them onto one cable, only one special cable
pair is needed to come from the CO as a feeder, instead of several separate
ones; this is why it is called a "pair gain" system. The remote terminal (RT)
contains both the demultiplexing electronics as well as a small "SAI" type
terminal block for connecting the pairs to distribution cables on the side
of the path toward the subscriber. Because the "feeder" is not a multipair
cable but a digital link (ie. T-carrier), this arrangement is known as a
"carrier-derived feeder." The SAI part of the RT is used just like a normal
SAI on the distribution side (BLUE), but the feeder side will be slightly
different. Carrier-derived feeders are always marked with YELLOW labels, and
their pairs will be crossed over to distribution cables just like in an SAI.
So, in order to access a pair in a system like this, you must do so on the
DISTRIBUTION side, because you can't hook an analog test set to a 1.544 Mbps
digital T-carrier line! (or worse yet, a fiber optic cable). This may be
difficult, because these cabinets are always locked (with few exceptions), so
you'll have to find a terminal closer to the subscriber -- also be aware that
many RT's are equipped with silent intrusion alarms. Anyway, some common
pair-gain systems are the Western Electric SLC-8, 40, 96, and GTE's MXU,
ranging in size from 8 to over 96 lines. RT cabinets can often be identified
by the ventillation grilles (with or without a fan inside) which are not
present on SAI's or other non-RT cabinets.
********************
-----------------------------------
Aerial Distribution Splice Closure,
Drop Wire Splitter
-----------------------------------
This terminal is the point where the individual cable pair for a
certain subscriber is split from the F2 distribution cable and spliced onto
an aerial drop or "messenger" wire which goes to the subscriber's premises.
In an aerial distribution plant, 2 types of this terminal are common:
1> Western Electric 49-type Ready Access Closure / Cable Terminal
2> Western Electric 53A4, N-type Pole Mount Cable Terminals
----------
Type 1> The 49-type, 1A1, 1B1, and 1C1 closures are all functionally similar.
This terminal is a semi-rectangular closure, about 15"L x 3"W x 5"H,
usually black, which is connected directly to the aerial cable itself;
it is coaxial with the cable, so the cable passes straight through it.
It splits up to 12 pairs from the distribution cable to a small bin-
ding post terminal block inside the closure. Aerial drop wires are
then connected to these binding posts, and the wires exit the term-
inal through holes on the bottom. These wires are strung via strain
relief clamps on the pole down to the subscriber's site. The terminal
closure is opened by pulling out and lifting either the whole cover
or the front panel after removing the cover fasteners on the bottom
and/or the sides (the closure is a thick neoprene cover over an alum-
inum frame). Inside the case, there is a terminal block and there
may be some sort of loading coil as well. The cable and this coil are
not openable, but the terminal block is. Since the F2 pair terminates
in this closure, the F2 BP number (cable/assignment data) corresponds
to a binding post on this terminal block. As mentioned earlier, this
terminal will also contain spare pairs, in case a subscriber wants
another line. In order to use one of these pairs, you must either get
an F2 (and then F1) CP number from LAC using the BP, or you can put a
trace tone on the pair at the aerial closure and then locate the pair
at the SAI. Then a cross-connect would have to be made to an active
F1 pair, and a drop wire (ughh) would have to be added back at the
aerial closure. Anyway, both the binding posts as well as the holes
(inside + out) are numbered left to right, so you may not even have
to open the closure if you are just looking for an F2 BP number --
just trace the drop wire from the house into the numbered hole on the
closure. The TErminal Address for the F2 is the address of the house
or premise closest to the pole near this closure. These terminals
(esp. 1A1, etc) are also used for straight and branch splices for
aerial cables, so you may see one cable in / two out; also, the
closure can be used for splicing only, so there may not be drop wires
(in this case, it wont be listed in LMOS because it is not a terminal
point). There is generally one of these every pole near a quad of
houses or so, mounted on the cable about an arm's length from the
pole.
Type 2> Both the 53A4 and the N-type terminals serve the same function as
the 49-type just described, except they are used in situations where
there are more than 4 houses (8 lines, including provisional pairs).
This terminal is mounted directly on the pole, about a foot down from
the aerial cable. It is not connected in line with the cable, so
there is no F2 splicing area in the cabinet (rather, a cable stub
comes from the terminal block and is spliced onto the span close to
where it touches the pole). It is about 22"H x 9"W x 4"D, rectan-
gular, and silver (unpainted). The door is similar to that of a 40-
type cabinet, but it's much smaller; it is opened using a 7/16" tool
in the same manner as before, except that the door must be lifted
before it can be opened or closed. In this way, the door slides down
on it's hinges when opened, so it locks in the open position and you
wont have to worry about it (especially nice because hanging onto a
pole is enough of a problem). The terminal block can handle from 25
to 50 pairs, with 32 holes in the back for aerial drop wires. Just
as in the Ready Access Closure, this is the F2 terminal, and the
numbered binding posts and holes correspond to F2 BP numbers. The
TEA will be the address nearest the terminal (just as before). This
terminal is common at the first pole on a street, on cul-de-sacs,
apartments, marinas & harbors, or anywhere there are many drop wires.
Buried Distribution Cross Box and Other Pedestals
-------------------------------------------------
This terminal serves the same function as the aerial closures, except
it is used in areas with a buried distribution plant. This cable assignment
for this terminal will be the F2 terminal, and the BP numbers and TEA will
be the same as for the aerial terminals. Probably the most common cross-boxes
are the PC4,6, and 12; these are around 50" tall by 4, 6, or 12" square respec-
tively, and they are painted gray-green like SAI cabinets. These are the
smallest pedestals in the distribution plant, and they don't have doors (they
look like waist-high square poles). In order to open one of these pedestals,
the two bolts on either side half way down the pedestal must be loosened with
a 7/16 hex wrench; then the front cover can be lifted up, out, and off the
rest of the closure. These terminals are located generally near small groups
of houses (up to about 12 lines usually) on the ground, often near other
utility cabinets (such as electric power transformers, etc). These are
becoming more common as the new housing tracts use buried distribution plant.
The F2 cable will enter as ! jable stub, and it is split into service wires
which go back underground to the subscribers.
All small pedestals are not necessarily the above type of terminal;
these pedestal closures are often used for other purposes, such as splicing
points in underground distribution, loading coil mounting, and even used as
temporary wire storage containers. If the terminal contains a terminal
block or it is a significant point on the line, however, it will be listed in
LMOS. An example of this is a distribution path found by Mark Tabas in a
Mountain Bell area -- there was a small PC12-type closure on the ground near
a street in a remote suburb, and it was serving as a terminal point for a
whole F1 cable. It was listed as the F1 terminal, and it was at the right
TEA; however, there was no terminal block because it was a splicing point
(just a bunch of pairs connected with Scotchlok plastic connectors which are
hung on a bar in the pedestal closure), so LMOS had no BP number. Instead,
a color code was listed (see appendix) for the pair in the splice. Anyway,
the WHOLE F1 went up to an N-type closure on a pole and was split into drop
wires.
--------------------------------------
Multi-Line Building Entrance Terminals
--------------------------------------
This terminal takes the aerial drop or service wires and cross-connects
them over to the Inside Wire (IW) in the subscriber's building (hotels, busi-
nesses, etc). There are many different types of terminal blocks for this
terminal, although by far the most common is the Western Electric 66 block.
The 66-type terminal uses a block of metal clips; the wire is pushed onto the
clip with a punch-down tool which also strips the wire. The block is divided
into horizontal rows which can have from 2 to over 6 clips each. Since each
row group terminates one pair, two rows are needed for x-connect, one on top of
the other. The service or drop wire usually enters on the left, and the
inside wire is connected to the far right. In order to locate a pair, usually
you can visually trace either the service wire or the inside wire to the
block, and often the inside wire side wil be numbered or labelled with an
address, phone number, etc. It is also possible for this terminal to serve
as an F2 terminal point, if there are a lot of lines. In this case, LMOS will
list the TEA usually with some physical direction as to where to find it. The
left side will then be numbered as F2 BP's. This terminal is also the demarca-
tion point which separates the customer's equipment from the telco's. The new
terminals often have an RJ-21 connector on the service wire side, such as a
25-pair for PABX or a Bell 1A2 Key, etc. There are also "maintenance termina-
ting units" (MTU) which are electronic units connected to the line(s) at the
entrance protector; these are sometimes seen in some telcos. Basically, they
provide functions such as party ANI on multi-party lines, remote disconnect
(for testing or (click!) non-payment), or half ringers (the most common --
they prevent ringing continuity failures on switches like ESS when there are
no phones hooked to the line when it rings). MTU terminals are often locked.
Single Pair Station Protector
-----------------------------
There's really not much to say about this terminal. Basically, it
takes the service or drop wire and connects it to the inside wire in a single
line residence (houses with 2 lines will have 2 of these). These are at every
house on an outside wall or basement, and there are two main types: the Western
Electric 123 (with a "150-type" rubber cover), and the old WE 305 and new AT&T
200 Network interface (metal and plastic, respectively). These terminals have
one binding post pair and they will have either gas discharge tubes or carbon
blocks to protect the line from lightning or excess current. Obviously, there
is no BP number (you just have to visually trace the drop wire to find the
protector). This is also the demarcation point marking the end of the telco's
responsibility, as well as the end of our tour.
********************
Bell System Standard Color Code Use:
----------------------------------- Take the #, and find it's closest
Pair # Tip Ring multiple of 5. Use that number to find
----------------------------------- the Tip color, and the remainder to find
01-05 White Blue the Ring color (remainder 0 = Slate).
06-10 Red Orange (e.g. Pair #1 = White/Brown, Pair #14 =
11-15 Black Green Black/Brown, Pair #24 = Violet/Brown).
16-20 Yellow Brown
21-25 Violet Slate
Usually if a color code is needed (such as in a splice case) you can get it
from LAC or the testboard; if it's really essential, it will be in LMOS as
well. This color code is also used a lot on cable ties (usually with white
stripes and ring colors only), although these are often used randomly.
---------
Test Sets
---------
This is the "right hand" of both the professional and the amatuer
lineman. Basically, it is a customized portable telephone which is designed
to be hooked onto raw cable terminals in the field and used to monitor the
line, talk, or dial out. The monitor function is usually the main difference
between the "butt-in" test set and the normal phone. If you don't have a
real test set already, the following circuit can convert a normal $4 made-in-
taiwan phone into a working test set. The "all-in-one" handset units without
bases are the best (I tend to like QUIK's and GTE Flip Phone II's). Anyway-
OFFICIAL Agent 04 Generic Test Set Modification (tm)
Ring >---------------------------------> to "test set" phone
Tip >------! SPST Switch !-------->
!-----/ ----------!
>from !-------/!/!/!/!--! C = 0.22 uF 200 WVDC Mylar
cable pair ! C R ! R = 10 kOhm 1/2 W
(alligators) !--! (------------! SPST = Talk / Monitor
When SPST is closed, you are in talk mode; when you lift the switch-
hook on the "test set" phone, you will get a dial tone as if you were a
standard extension of the line you are on. You will be able to dial out and
receive calls. When the SPST is opened, the resistor and capacitor are no
longer shunted, and they become part of the telephone circuit. When you lift
the switchhook on the test set, you will not receive dial tone, due to the fact
that the cap blocks DC, and the resistor passes less than 4 mA nominally (far
below the amount necessary to saturate the supervisory ferrod on ESS or close
the line relay on any other switch). However, you will be able to silently
monitor all audio on the line. The cap reactance + the phone's impedance
insure that you won't cut the signal too much on the phone line, which might
cause a noticeable change (..expedite the shock force, SOMEONE'S ON MY LINE!!).
It's also good to have a VOM handy when working outside to rapidly check for
active lines or supervision states. Also, you can buy test equipment from
these companies:
Techni Tool - 5 Apollo Road, Box 368. Plymouth Meeting, PA. 19462.
Specialized Products Company - 2117 W. Walnut Hill Lane, Irving, TX. 75229.
********************
I am not going to include a disclaimer, because a true communications
hobbyist does not abuse nor does he tamper with something he doesn't under-
stand. This article is intended as a reference guide for responsible people.
Also, this article was written mainly from first-hand experience and
information gained from maintenance technicians, test boards, as well as
technical literature, so it is as accurate as possible. Keep in mind that
it is mainly centered upon the area served by Pacific Telephone, so there may
be some differences in the loop plant of your area. I would be happy to
answer the questions of anyone interested, so feel free to contact me c/o the
Technical Journal regarding anything in this article or on related topics such
as ESS, loop electronics, telephone surveillance / countersurveillance, etc.
I hope the article was informative.
--------------------------------
Written by: Phucked
Agent
04
The Legion Of Doom!
--------------------------------
Please - Por Favor - Bitte - Veuillez!
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