The LOD/H Technical Journal: File #8 of 12

*** NOTE ***





                            The Legion of Doom!



                        LOD Reference Guide  Vol. I

                      Outside Loop Distribution Plant


                      Written 12/86       Phucked

                      Revision III          Agent






        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.



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.



        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

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.


End of First half, attach second half here.

The LOD/H Technical Journal: File #9 of 12

 *** Second half of The Outside Loop Distribution Plant starts here. ***


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 standard 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


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 a cable 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



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



             The Legion Of Doom!


Please - Por Favor - Bitte - Veuillez!

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