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.:: Busy Line Verification Part II ::.

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Current issue : #12 | Release date : 1987-03-29 | Editor : Taran King
Index of Phrack 12Taran King
Pro-Phile IX on Agrajag The ProlongedTaran King
Preview to Phrack 13-The Life & Times of The ExecutionerThe Executioner
Understanding the Digital Multiplexing System (DMS)Control C
The Total Network Data SystemDoom Prophet
CSDC II - Hardware RequirementsThe Executioner
Hacking : OSL SystemsEvil Jay
Busy Line Verification Part IIPhantom Phreaker
Scan Man's Rebuttal to Phrack World NewsScan Man
Phrack World News XII Part IKnight Lightning
Phrack World News XII Part IIKnight Lightning
Title : Busy Line Verification Part II
Author : Phantom Phreaker
                               ==Phrack Inc.==

                     Volume Two, Issue 12, Phile #8 of 11

                        BUSY LINE VERIFICATION PART II

                         WRITTEN BY PHANTOM PHREAKER

    This file is meant to be an addition to the first file that was included
in Phrack Inc. Issue XI. It is assumed that the reader has read and understood
the previous file.  Most of this information will be taken from Bell System
Publications so you don't have to worry about it being incorrect.

    First off, I'd like to correct a minor error included in the first file. I
use the format 'KP+0XX+PRE+SUFF+ST' to show the MF routing that is used. This
is not correct AT&T syntax though, the correct format is KP+0XX+NXX+XXXX+ST.
This is minor detail, but some people are very picky.

The Verification Network

    In a TSPS office, a verification circuit is associated with a 4-wire
OutGoing Trunk (OGT) and a 3-way/4-wire bridging repeater arrangement. This is
the circuit that does the speech scrambling. The speech and other tones (like
busy and re-order) are frequency shifted, but are still recognizable by a TSPS

    TSPS verification trunks are connected via dedicated lines to incoming
verification trunks in a toll office. The toll office provides either a link
to an outgoing trunk and dedicated facilities to another toll office, or an
outgoing toll connecting trunk and dedicated facilities to an incoming
verification trunk in a local office. Each toll office has ways to check the
security of verification trunks. In electronic toll offices (ESS offices), two
independent office data translations provide security of the trunk. Electro-
mechanical toll offices (Such as a CrossBar Tandem (XBT)) use an electrical
cross-office check signal or a segregated switching train to control trunk
connections. Verification trunks relay supervisory signals (such as answering
supervision) to TSPS from the line being verified. Also, if verification
trunks are busy, the TSPS operator will receive a re-order.

The functions of the VFY key

    When the operator presses the VFY key, several checks are made upon the
number that has been entered. These are:
    A Check to see if the line is within the verification network accessible
by that particular TSPS. If the line is not, the VFY key will flash.

    A check to see if the owner of the line wishes BLV to be possible or not.
If the line is something like a police emergency line, then the VFY key will
flash, similar to the first check.

Important TSPS keys

    When the VFY lamp lights steady (doesn't flash), indicating the process is
acceptable, the operator puts the calling customer on hold and accesses an
idle loop on the operator position. The ACS (Access) lamp lights steady if a
verification trunk is available at that time. Then, the operator presses the
ST key which sends out the complete number to be verified, in MF. The
verification circuit activates, and the operator listens for scrambled speech
and also watches the CLD (Called) lamp on her console. The CLD lamp is lighted
when the operator loop was accessed, and will remain lit if the line being
verified is on-hook. The operator has two ways of seeing if the line is in
use, by listening, and by watching the CLD lamp. If the CLD lamp light goes
out, then the line is off-hook.

    If a successful BLV/EMER INT is performed, the operator presses the REC
MSG MSG (Record Message) key, which completes the verification. If the EMER
INT lamp is lit, the charges for the interrupt and the verification are
automatically billed. If the VFY key is pressed twice, it indicates the
verification should not be billed. This could be due to a customer error or a
customer disconnect.

Charging capabilities

    A customer can pay for a BLV/EMER INT in several ways. They can have the
charges put on their phone bill, if they are calling from their home, they can
bill the charges to an AT&T Calling Card, or pay directly from a coinphone.
Details of the BLV/EMER INT function are recorded on AMA tape, which is later
processed at the RAO (Revenue Accounting Office).

    The classes of charge are as follows: STATION PAID, which means exactly
what it says, STATION SPECIAL CALLING, in cases where billing is handled by a
Calling Card or third number billing, and NO AMA, in unusual billing cases.

    Also, for BLV/EMER INT calls that originate from a hotel, TSPS can send
charges to HOBIS (Hotel Billing Information System), HOBIC (Hotel Billing
Information Center), or a TTY at the hotel.

    AMA records for BLV/EMER INT are recorded in basically the same format
that normal calls are recorded. The only difference is that a numeric data
group is added. The leftmost digit in the data group is a 1 if only a BLV was
done, but it is a 2 if both a BLV and an EMER INT were done. In case of an
aborted BLV, the billing record is marked 'No charge'.

Inward Operator differences

    When an Inward operator does BLV/EMER INT, the class of charge is always
NO AMA, because billing is handled at the local TSPS site. Inwards also do not
use the REC MSG key when a TSPS would, they use the VFY key in it's place.

The Speech scrambling technique

    The speech scrambling technique that exists to keep the customers privacy
intact is located in the TSPS console, and not in the verification trunks. The
scrambling technique can only be deactivated by an operator pressing the EMER
INT key, or a craftsperson using the console in a special mode. When the
scrambler is deactivated by an operator doing an EMER INT, the customer hears
an alerting tone (as mentioned in the first BLV file) made up of a 440Hz tone.
This tone is initially played for two seconds, and then once every ten seconds
afterwards until the operator presses her Position Release (POS RLS) key.

Operator trouble reporting

    When operators have trouble in handling a call, they can enter trouble
reports that are technically called 'Operator keyed trouble reports'. These
cause messages to be printed on the maintenance TTY and on the trouble report
TTY channel. There are different trouble codes for different things, such as
trouble with the speech scrambler, trouble in the verification network, or
trouble in collecting charges from a customer.

    In my area there are 20 such TSPS trouble codes. These are done in MF.
They are entered with the KP TRBL (Key Pulse Trouble) key followed by a two
digit trouble code followed by an ST. A trouble code for beeper trouble could
be entered as KP TRBL+62+ST, and speech scrambler trouble could be KP
TRBL+89+ST. Some of the other reasons for trouble codes are: Crosstalk, No
ring, Noisy, can't hear, improper supervision toward the called and calling
parties, cutoff, positions crossed, coin collecting trouble, third re-order,
distant operator no answer, echo, data transmission, no answer supervision, ST
key lit for more than 4 seconds, and others for person-to-person and
station-to-station completed collect calls.

Maintenance and traffic measurements

    These reports can be output from a maintenance or engineering and service
data TTY, daily or hourly. Each daily report contains data for the previous
day. Some traffic counts are as follows:
    Total Verification attempts, VFY key depressions, VFY key depressions when
the requested number is out of TSPS range, VFY key depressions in which the
requested number wasn't verifiable, BLV trunk seizures which pass an
operational test, and EMER INT attempts. Other traffic counts include the
measurements for usage of BLV trunks, the amount of time BLV trunks were
unavailable, and the number of times BLV trunks were seized.

    I hope this file has helped people further understand how the BLV system
works. If you haven't read part I, get a copy of Phrack Inc. Issue XI and read
file #10.

    As said earlier, most of this information comes directly from Bell System
Publications and so it should be viewed as correct. However, if you do find
any errors then please try to let me know about them so they can be corrected.

Suggested reading

TSPS Part I: The console-Written by The Marauder, LOD/H Technical Journal
Issue No. 1, file #4

Busy Line Verification-Phrack Issue XI, file #10

Busy Verification Conference Circuit-Written by 414 Wizard

Verification-TAP issue 88, Written by Fred Steinbeck

Bell System Technical Journal, Vol. 59, No 8.
Bell Labs RECORD periodical

And the following people for contributing information in some form:

Mark Tabas, Doom Prophet, The Marauder
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