How Ma Bell Works by the Jolly Roger

In this article, I will first describe the termination,

wiring, and terminal hardware most commonly used in the Bell

system, and I will include section on methods of using them.




The local telephone network between the central

office/exchange and the telephone subscribers can be briefly

described as follows:

From the central office (or local exchange) of a certain

prefix(es), underground area trunks go to each area that has that

prefix (Usually more than one prefix per area.) At every few

streets or tract areas, the underground cables surface. They then

go to the telephone pole (or back underground, depending on the

area) and then to the subsribers house (or in the case of an

apartment building or mutliline business, to a splitter or dis-

tribution box/panel).

Now that we have the basics, I'll try and go in-depth on the





These are sometimes inter-office trunks, but usually in a

residential area they are trunk lines that go to bridging heads

or distribution cases. The cables are about 2-3 inches thick

(varies), and are either in a metal or pvc-type pipe (or

similiar). Rarely (maybe not in some remote rural areas) are the

cables just 'alone' in the ground. Instead they are usually in

an underground cement tunnel (resembles a small sewer or storm-

drain.) The manholes are >heavy< and will say 'Bell system' on

them. they can be opened with a 1/2 inch wide crowbar (Hookside)

inserted in the top rectangular hole. There are ladder rungs to

help you climb down. You will see the cable pipes on the wall,

with the blue and white striped one being the inter-office trunk

(at least in my area). The others are local lines, and are

usually marked or color coded. There is almost always a posted

color code chart on the wall, not to mention Telco manuals de-

scribing the cables and terminals, so I need not get into detail.

Also, there is usually some kind of test equipment, and often

Bell test sets are left in there.




The innocent-looking grayish-green boxes. These can be

either trunk bridges or bridging for residences. The major trunk

bridging heads are usually larger, and they have the 'Western

Electric' logo at the bottom, whereas the normal bridging heads

(which may be different in some areas-depending on the company

you are served by. GTE B.H.'s look slightly different. Also, do

not be fooled by sprinkler boxes!) They can be found in just

about every city.

To open a bridging head: if it is locked (and you're feeling

destructive), put a hammer or crowbar (the same one you used on

the manhole) in the slot above the top hinge of the right door.

Pull hard, and the door will rip off. Very effective! If it isn't

locked (as usual), take a 7/8 inch hex socket and with it, turn

the bolt about 1/8 of a turn to the right (you should hear a

spring release inside). Holding the bolt, turn the handle all the

way to the left and pull out.

To Check for a test-set (which are often left by Bell employees),

go inside - First check for a test-set (which are often left

by Bell employees). There should be a panel of terminals and

wires. Push the panel back about an inch or so, and rotate the

top latch (round with a flat section) downward. Release the

panel and it will fall all the way forward. There is usually a

large amount of wire and extra terminals. The test-sets are

often hidden here, so don't overlook it (Manuals, as well, are

sometimes placed in the head). On the right door is a metal box

of alligator clips. Take a few (Compliments of Bell.). On each

door is a useful little round metal device. (Says 'insert gently'

or' clamp gently - do not overtighten' etc..) On the front of

the disc, you should find two terminals. These are for your test

set. (If you dont have one, dont despair -I'll show you ways to

make basic test sets later in this article).

Hook the ring (-) wire to the 'r' terminal; and the tip (+)

wire to the other. (By the way, an easy way to determine the

correct polarity is with a 1.5v LED. Tap it to the term. pair,

if it doesnt light, switch the poles until it does. When it

lights,find the longer of the two LED poles: This one will be on

the tip wire (+). Behind the disc is a coiled up cord. This

should have two alligator clips on it.. Its very useful, because

you dont have to keep connecting and disconnecting the fone (test

set) itself, and the clips work nicely.

On the terminal board, there should be about 10 screw

terminals per side. Follow the wires, and you can see which

cable pairs are active. Hook the clips to the terminal pair, and

you're set! Dial out if you want, or just listen (If someone's

on theline). Later, I'll show you a way to set up a true 'tap'

that will let the person dial out on his line and receive calls

as normal, and you can listen in the whole time. More about this


On major prefix-area bridging heads, you can see 'local

loops' ,which are two cable pairs (cable pair = ring+tip, a fone

line) that are directly connected to each other on the terminal

board. These 'cheap loops' as they are called, do not work

nearLy as well as the existing ones set up in the switching

hardware at the exchange office. (Try scanning your prefixes'

00xx to 99xx #'s.) The tone sides will announce themselves with

the 1008 hz loop tone, and the hang side will give no response.

The first person should dial the 'hang' side, and the other

person dial the tone side, and the tone should stop if you have

got the right loop.)

If you want to find the number of the line that you're on,

you can either try to decipher the 'bridging log' (or whatever),

which is on the left door. If that doesnt work, you can use the



ANI # (Automatic Number ID)


This is a Telco test number that reports to you the number

that youre calling from (It's the same, choppy 'Bell bitch' voice

that you get when you reach a disconnected #)

For the 213 NPA - Dial 1223

408 NPA - Dial 760

914 NPA - Dial 990

These are extremely useful when messing with any kind of line

terminals, house boxes, etc.

Now that we have bridging heads wired, we can go on... (don't

forget to close and latch the box after all... Wouldnt want GE

and Telco people mad, now, would we?)


"CANS" - Telephone Distribution Boxes



Basically, two types:

1> Large, rectangular silver box at the end of each street.

2> Black, round, or rectangular thing at every telephone pole.

Type 1 - This is the case that takes the underground cable from

the bridge and runs it to the telephone pole cable (The lowest,

largest one on the telephone pole.) The box is always on the

pole nearest the briging head, where the line comes up. Look for

the 'Call before you Dig - Underground cable' stickers..

The case box is hinged, so if you want to climb the pole,

you can open it with no problems. These usually have 2 rows of

terminal sets.

You could try to impersonate a Telco technician and report

the number as 'new active' (giving a fake name and fake report,

etc.) I dont recommend this, and it probably won't (almost

positively won't) work, but this is basically what Telco linemen


Type 2 - This is the splitter box for the group of houses around

the pole (Usually 4 or 5 houses). Use it like I mentioned

before. The terminals (8 or so) will be in 2 horizontal rows of

sets. The extra wires that are just 'hanging there' are

provisions for extra lines to residences (1 extra line per house,

thats why the insane charge for line #3!) If its the box for

your house also, have fun and swap lines with your neighbor!

'Piggyback' them and wreak havoc on the neighborhood (It's

eavesdropping time...) Again, I don't recommend this, and its

difficult to do it correctly. Moving right along...





Found outside the buliding (most often on the right side,

but not always... Just follow the wire from the telephone pole)

or in the basement. It has a terminal for all the lines in the

building. Use it just like any other termination box as before.

Usually says 'Bell system' or similar. Has up to 20 terminals on

it (usually.) the middle ones are grounds (forget these). The

wires come from the cable to one row (usually the left one), with

the other row of terminals for the other row of terminals for the

building fone wire pairs. The ring (-) wire is usually the top

terminal if the set in the row (1 of 10 or more), and the tip is

in the clamp/screw below it. This can be reversed, but the cable

pair is always terminated one-on-top-of-each- other, not on the

one next to it. (I'm not sure why the other one is there,

probably as aprovision for extra lines) Don't use it though, it

is usually to close to the other terminals, and in my experiences

you get a noisy connection.

Final note: Almost every apartment, business, hotel, or anywhere

there is more than 2 lines this termination lines this

termination method is used. If you can master this type, you can

be in control of many things... Look around in your area for a

building that uses this type, and practice hooking up to the

line, etc.

As an added help,here is the basic 'standard' color-code for

multiline terminals/wiring/etc...

Single line: Red = Ring

Green = Tip

Yellow = Ground *

* (Connected to the ringer coil in individual and bridged

ringer phones (Bell only) Usually connected to the green


Ring (-) = Red

White/Red Stripe


White/Orange Stripe

Black/Yellow Stripe

Tip (+) = Green (Sometimes

yellow, see above.)

White/Green Stripe

White/Blue Stripe


Black/White Stripe

Ground = Black





Small, gray (can be either a rubber (Pacific Telephone) or hard

plastic (AT & T) housing deal that connects the cable pair from

the splitter box (See type 2, above) on the pole to your house

wiring. Only 2 (or 4, the 2 top terminals are hooked in parallel

with the same line) terminals, and is very easy to use. This can

be used to add more lines to your house or add an external line

outside the house.




Well, now you can consider yourself a minor expert on the

terminals and wiring of the local telephone network. Now you can

apply it to whatever you want to do.. Here's another helpful


How to make a Basic Test-Set and how to use it to dial out,

eavsdrop, or seriously tap and record line activity.

These are the (usually) orange hand set fones used by Telco

technicians to test lines. To make a very simple one, take any

Bell (or other, but I recommend a good Bell fone like a princess

or a trimline. gte flip fones work excllently, though..) fone and

follow the instructions below.

Note: A 'black box' type fone mod will let you tap into their

line, and with the box o, it's as if you werent there. they can

recieve calls and dial out, and you can be listening the whole

time! very useful. With the box off, you have a normal fone test



A basic black box works well with good results. Take the cover

off the fone to expose the network box (Bell type fones only).

The <RR> terminal should have a green wire going to it (orange or

different if touch tone - doesnt matter, its the same thing).

Disconnect the wire and connect it to one pole of an SPST switch.

Connect a piece of wire to the other pole of the switch and

connect it to the <RR> terminal. Now take a 10k hm 1/2 watt 10%

resistor and put it between the <RR> terminal ad the <F>

terminal, which should have a blue and a white wire going to it

(different for touch tone). It should look like this:

-----Blue wire----------<F>


----White wire-----!


10k Resistor



--Green wire-- !----<RR>

! !


What this does in effect is keep the hookswitch / dial pulse

switch (F to RR loop) open while holding the line high with the

resistor. This gives the same voltage effect as if the fone was

'on-hook', while the 10k ohms holds the voltage right above the

'off hook' threshold (around 22 volts or so, as compared to 15-17

or normal off hook 48 volts for normal 'on-hook'), giving

Test Set Version 2.

Another design is similar to the 'type 1' test set (above),

but has some added features:

From >----------------Tip------<To Test

Alligator set

Clip >----------------Ring-----<phone

! !

x !

! !

o !

! x---RRRRR---!

! x !

!---x !


x = Spst Switch

o = Red LOD 0 = Green LED

RRRRR= 1.8k 1/2 watt xxxx= Dpst switch


When the SPST switch in on, the LED will light, and the fone

will become active. The green light should be on. If it isn't,

switch the dpst. If it still isnt, check the polarity of the

line and the LEDs. With both lights on, hang up the fone. They

should all be off now. Now flip the dpst and pick up the fone.

The red LED shold be on, but the green shouldnt. If it is,

something is wrong with the circuit. You wont get a dial tone if

all is correct.

When you hook up to the line with the alligator clips

(Assuming you have put this circuit inside our fona and have put

alligator clips on the ring and tip wires (As we did before)) you

should have the spst #1 in the off posistion. This will greatly

reduce the static noise involved in hooking up to a line. The red

LED can also be used to check if you have the correct polarity.

With this fone you will have the ability to listen in on

>all< audible line activity, and the people (the 'eavesdropees')

can use their fone as normal.

Note that test sets #1 and #2 have true 'black boxes', and can be

used for free calls (see an article about black boxes).


Test Set Version 3


To do test set 3:

Using a trimline (or similar) phone, remove the base and cut

all of the wire leads off except for the red (ring -) and the

green (tip +). Solder alligator clips to the lug. The wire

itself is 'tinsel' wrapped in rayon, and doesnt solder well.

Inside the one handset, remove the light socket (if it has one)

and install a small slide or toggle switch (Radio Shack's micro-

miniature spst works well). Locate the connection of the ring

and the tip wires on the pc board near where the jack is located

at the bottom of the handset. (The wires are sometimes black or

brow instead of red and green, respectively). Cut the foil and

run 2 pieces of wire to your switch. In parallel with the switch

add a .25 uf 200 VDC capacitor (mylar, silvered mica, ceramic,

not an electrolytic). When the switch is closed, the handset

functions normally. With the switch in the other position, you

can listen without being heard.

Note: To reduce the noise involved in connecting the clips to a

line, add a switch selectable 1000 ohm 1/2 watt resistor in

series with the tip wire. Flip it in circuit when connecting, and

once on the line, flip it off again. (or just use the 'line disc-

onect' type switch as in the type 2 test set (above)). Also

avoid touching the alligator clips to any metal parts or other

terminals, for i causes static on the line and raises poeple's





If you would like to record any activity, use test set 1 or

2 above (for unattended recording of >all< line activity), or

just any test set if you are going to be there to monitor when

they are dialing, talking, etc.

Place a telephone pickup coil (I recommend the Becoton T-5 TP

coil or equivalent) onto the test set, and put the TP plug into

the mic. jack of any standard tape recorder. Hit play, rec, and

pause. Alternate pause when you want to record (I dont think

anyone should have any difficulty with this at all...)

Well, if you still can't make a test set or you dont have the

parts, there's still hope. Alternate methods:

1> Find a bell test set in a manhole or a bridging head and

'Borrow it indefinately...

2> Test sets can be purchased from:


5 Apollo Road

Box 368

Plymouth Meeting PA., 19462

Ask for catalog #28

They are usually $300 - $600, and are supposed to have MF

dialing capability as well as TT dialing. They are also of much

higher quality than the standard bell test sets.

If you would like to learn more about the subjects covered here,

I suggest:

1> Follow Bell trucks and linemen or technicians and ask subtle

questions. also try 611 (repair service) and ask questions..

2> Explore your area for any Bell hardware, and experiment with

it. Don't try something if you are not sure what youre doing,

because you wouldnt want to cause problems, would you?