Vital Ingredients: Switching Centers and Operations

by BIOC Agent 003

Every switching office in North America (the NPA system), is assigned an office name and class.  There are five classes of offices numbered 1 through 5.  Your CO is most likely a Class 5 or end office.

All long-distance (toll) calls are switched by a toll office which can be a Class 4, 3, 2, or 1 office.  There is also a 4X office called an intermediate point.  The 4X office is a digital one that can have an unattended exchange attached to it (known as a Remote Switching Unit - RSU).

The following chart will list the office number, name, and how many of those offices existed in North America in 1981:

Class Name Abbr. # Existing 1 Regional Center RC 12 2 Sectional Center SC 67 3 Primary Center PC 230 4 Toll Center TC 1,300 4P Toll Point TP 4X Intermediate Pt IP 5 End Office EO 19,000 R RSU RSU

When connecting a call from one party to another, the switching equipment usually tries to find the shortest route between the Class 5 end office of the caller and the Class 5 end office of the called party.

If no inter-office trunks exist between the two parties, it will then move up to the next highest office for servicing (Class 4).  If the Class 4 office cannot handle the call by sending it to another Class 4 or Class 5 office, it will be sent to the next office in the hierarchy (3).

The switching equipment first uses the high-usage inter-office trunk groups, if they are busy it then goes to the final trunk groups on the next highest level.  If the call cannot be connected then, you will probably get a re-order (120 IPM [Interruptions Per Minute] signal - also known as fast busy ).

At this time, the guys at Network Operations are probably shitting in their pants and trying to avoid the dreaded Network Dreadlock (as seen on TV!).

It is also interesting to note that nine connections in tandem is called "ring-around-the rosy" and it has never occurred in telephone history.  This would cause an endless loop connection.  (An interesting way to really screw up the network.)

The ten regional centers in the U.S. and the two in Canada are all interconnected.  They form the foundation of the entire telephone network.  Since there are only twelve of them, they are listed below:

Class 1 Regional Office Location NPA Dallas 4ESS 214 Wayne, PA 215 Denver 4T 303 Regina No.2 SP1-4W [Canada] 306 St. Louis 4T 314 Rockdale, GA 404 Pittsburgh 4ESS 412 Montreal No.1 4AETS [Canada] 504 Norwich, NY 607 San Bernardino, CA 714 Norway, IL 815 White Plains 4T, NY 914

(Old Number 4 Crossbar (#4XB) Tandem List)

In the network, there are three major types of switching equipment.  They are known as: step, crossbar, and ESS.  Check past and future issues of 2600 for complete details on how these systems work.

Operators

Another vital ingredient of the network is the telephone operator.  There are many different kinds.  What follows is a discussion of some of the more common ones.

TSPS Operator:  The Traffic Service Position System (TSPS), as opposed to This Shitty Phone Service operator is probably the bitch (or bastard for the phemale liberationists) that most of us are use to having to deal with.

Here are her responsibilities:

1. Obtaining billing information for calling card or third-party phone calls.
2. Identifying called customer on person-to-person calls.
3. Obtaining acceptance of charges on collect calls.
4. Identifying calling numbers.  This only happens when the calling number is not automatically recorded by Centralized Automatic Message Accounting (CAMA) and forwarded from the local office.  This could be caused by equipment failures (ANIF - Automatic Number Identification Failure) or if the office is not equipped for CAMA (ONI - Operator Number Identification).

(I once had an equipment failure happen to me and the TSPS operator came on and said, "What number are you calling from?"  Out of curiosity, I gave her the number to my CO, she thanked me and then I was connected to a conversion that appeared to be between a frameman and his wife.  Then it started ringing the party I originally wanted to call and everyone phreaked out (excuse the pun).  I immediately dropped this dual line conference!)

You shouldn't mess with the TSPS operator since she knows where you are calling from.  Your number will show up on a 10-digit LED read-out (ANI board).  She also knows whether or not you are at a fortress fone and she can trace calls quite readily.  Out of all the operators, she is one of the most dangerous!

INWARD Operator:  This operator assists your local TSPS ("0") operator in connecting calls.  She will never question a call as long as the call is within her service area.  She can only be reached via other operators or by a Blue Box.  From a Blue Box, you would dial KP + NPA + 121 + ST for the INWARD operator that will help you connect any calls within that NPA only.

Directory Assistance Operator:  This is the operator that you are connected to when you dial 411 or NPA-555-1212.  She does not readily know where you are calling from.  She does not have access to unlisted numbers, but she does know if an unlisted number exists for a certain listing.

There is also a directory assistance for deaf people who use teletypewriters (TTY).  If your modem can transfer Baudot (45.5 baud - the Apple-CAT can), then you can call him/her up and have an interesting conversation.  The number is: 800-855-1155.  They uses the standard Telex abbreviations such as GA for Go Ahead.  They tend to be nicer and will talk longer than your regular operators.  Also, they are more likely to be persuaded to give more information through the process of "social engineering."

(Unfortunately, they do not have access to much.  I once bullshitted with one of these operators and I found out that there are two such DA offices that handle TTY.  One is in Philadelphia and the other is in California.  They have approximately seven operators each.  Most of the TTY operators think their job is boring.   They also feel they are underpaid.  They actually call up a regular DA number to process your request - no fancy computers here!  (Other operators have access to their own DA by dialing: KP + NPA + 131 + ST)

The TTY directory assistance, by the way, is still a free call, unlike normal DA.  One might be able to avoid being charged for DA calls by using a computer and modem at 45.5 baud.

CN/A Operators:  CN/A operators are operators that do exactly the opposite of what directory assistance operators are for.  You give them the number, they give you the name and address.  In my experiences, these operators know more than the DA operators do and they are more susceptible to "social engineering."  It is possible to bullshit a CN/A operator for the NON-PUB DA number (i.e., you give them the name and they give you the unlisted number).  This is due to the fact that they assume your are a phellow company employee.  The divestiture, though, has resulted in the breakup of a few NON-PUB numbers and policy changes in CN/A.

Intercept Operator:?  The intercept operator is the one that you are connected to when there are not enough recordings available to tell you that the number has been disconnected or changed.  They usually say, "What number did you dial?"  This is considered the lowest operator lifeform since they have no power whatsoever and usually know very little.

Other Operators:  And then there are the: Mobile, Ship-to-Shore, Conference, Marine Verify, "Leave Word and Call Back," Route and Rate (KP + 800 + 141 + 1212 + ST - new number as result of Bell breakup), and other special operators who have one purpose or another in the network.

Problems with an operator?  Ask to speak to their supervisor... or better yet, the Group Chief (who is the highest ranking official in any office) who is the equivalent of the Madame in a whorehouse (if you will excuse the analogy).

Some COs, by the way, have bugs in them that allow you to use a 1 or 0 as the 4^th digit when dialing.  (This tends to happen mostly in crossbars and it doesn't work consistently).  This enables a caller to call special operators and other internal telco numbers without having to use a Blue Box.  For example, 415-121-1111 would get you a San Francisco-Oakland INWARD operator.

The above was taken from Basic Telecommunications - Part IV written by BIOC Agent 003.)