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From: egurney@vcd.hp.com (Eddy J. Gurney)
Subject: FAQ: rec.video.cable-tv FYI List (09/21/93)
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--Editors note: no changes since last posting.


           ::::::::::::::::::::::::::::::::::::::::::::::::::
           :        The rec.video.cable-tv FYI* list!       :
           ::::::::::::::::::::::::::::::::::::::::::::::::::
                        * For Your Information

                    Last updated September 21, 1993
         (Added information on Scientific-Atlanta product line,
         a short blurb on Oak Sigma scrambling, and several new
                        terms to the glossary.)

    Feel free to mail me any additional information, additions or
       corrections, but PLEASE DO NOT E-MAIL ME ASKING FOR MORE 
     INFORMATION.  If something is not listed here, I don't know 
                enough about it to comment any further. 

________________________________________________________________________

Note that this information has been collected from magazines, various
posts to many UseNet groups over the past several years, etc.  I do not
have any personal experience with this stuff (which is why it may
seem so vague in places where I've only heard bits and pieces about it)
but at least it's a start.  All standard disclaimers apply.

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 
____________________________IMPORTANT_NOTICE____________________________

The ownership of a signal descrambler does NOT give the owner the right
to decode or view any scrambled signals without authorization from the
proper company or individual.  Use of such a device without permission
may be in violation of state and/or federal laws.  The information
contained herein is intended to serve as a technical aid to those person
seeking information on various scrambling techniques.  No liability by
myself or my employer is assumed for the (mis)use of this information. 
________________________________________________________________________
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 

{Note: Someone recommended a book called "Satellite TV Descrambling" by 
Sheets/Graf.  I've never seen it, but it may be of interest to some.}

_________________________Scrambling_Technologies________________________

................No Scrambling (Traps/Addressable Taps)..................
A cable system may not be scrambled at all. Some older systems (and many
apartment complexes) use "traps" or "filters" which actually REMOVE the
signals you aren't paying for from your cable. (These are negative traps
because they remove the WHOLE signal.) These systems are relatively
secure because the traps are often located in locked boxes, and once
a service technician finds out they're missing or have been tampered
with (by pushing a pin through a coax trap it to change its frequency,
for example), it's a pretty solid piece of evidence for prosecution.
Another method is where the head-end ADDS an extraneous signal about
2.5 MHz above the normal visual carrier which causes a tuner to think
its receiving a very strong signal--the tuner then adjust the automatic
gain control and buries the real signal. If you pay for the service, the
cable company adds a "positive trap" which then REMOVES the extraneous
injected signal so it becomes viewable. (This system is very easy to
circumvent by building your own notch filter, so it is not very commonly
used.) Advantages to a cable system with this technology is that you
don't need a cable box--all your cable-ready TVs, VCRs, etc. will all
work beautifully. The disadvantage is that pay-per-view events are not
possible, and that every time someone requests a change in service, a
technician has to be dispatched to add/remove the traps.

Becoming more and more popular, not only because of the Cable Act of
1992 but also in an effort to stop "pirates" are addressable taps. Many
cable companies WILL be moving to this technology in the near future.
These are devices located at the pole, where your individual cable feed
is tapped from the head-end. Similar to addressable converters, they
each have a unique ID number and can be turned on/off by a computer at
the head-end. Any stations which you are not paying for are filtered
out by electronicly switchable traps in the units. (Including the whole
signal if you haven't paid your bill or had the service disconnected.)
{Several patents have already been issued for various methods of making
SURE you don't see a channel you don't pay for.} Again, these almost
GUARANTEE an end to piracy and don't have any of the disadvantages
of the manual traps. Plus, they provide a superior signal to those
customers paying for service because they no longer need complicated
cable boxes or A/B switches -- and they can finally use all of the
"cable-ready" capabilites of the VCR, TV, etc. About the only known
attack on this type of system is to splice into a neighbors cable, which
again provides plenty of physical evidence for prosecution.

...............................Sine-Wave................................
Early Oak (and some very early Pioneer boxes) employed a sine-wave sync
suppresion system. In this system, the picture would remain vertically
stable, but wiggling black bars with white on either side would run
down the center of the screen. The lines were caused by a 15,750 Hz
sine-wave being injected with the original signal, causing the sync
separator in the TV to be unable to detect and separate the sync pulses.
Later, Oak came out with a "Vari-Sync" model, which also removed a
31,500 Hz sine-wave added to the signal. Oak was one of the first to
use extra signals ("tags") as a counter-measure for pirate boxes -- in
the normal mode, a short burst of a 100 KHz sine-wave (the tag signal)
would be sent during the VBI, along with the AM sine-wave reference
on the audio carrier and scrambled video. They would then put the AM
sine-wave reference signal onto the audio carrier, leave the video
alone, and NOT send the tag. Any box which simply looked for the AM
sine-wave reference would effectively scramble the video by adding a
sine-wave to the unscrambled video! Real decoders looked for the tag
signal and still worked correctly. Other combinations of tag/no tag,
scrambled/unscrambled video were also possible.

.....................6 dB In-Band Sync Suppression......................
Early Jerrold boxes used in-band gated sync suppression. The horizontal
blanking interval was suppressed by 6 dB. A 15.734, 31.468 or 94.404
KHz reference signal (conveniently all even multiples of the horizontal
sync frequency) was modulated on the sound carrier of the signal, and
used to reconstruct the sync pulse. An article in February 1984 issue
of Radio-Electronics explains this somewhat-old technique. Converters
which have been known to use this system include the Scientific-Atlanta
8500-321/421, a number of Jerrold systems [see numbering chart], Jerrold
SB-#, SB-#-200, SB-#A, RCA KSR53DA, Sylvania 4040 and Magnavox Magna
6400.

...................Tri-mode In-Band Sync Suppression....................
A modification to the 6dB sync suppresion system, dubbed "tri-mode",
allows for 0, 6 and 10 dB suppression of the horizontal sync pulse. The
three sync levels can be varied at random (as fast as once per field),
and the data necessary to decode the signal is contained in unused lines
during the VBI (along with other information in the cable data stream.)
See the February 1987 issue of Radio-Electronics for a good article
(both theory and schematics) on the tri-mode system. Converters which
have been known to use this system include a number of Jerrold systems
[see numbering chart], Jerrold SBD-#A, SBD-#DIC, Jerrold Starcom VI
(DP5/DPV models), Regency, Scientific- Atlanta 8550-321 {anyone know any
others for sure?} and early Pioneer systems {anyone know for sure which
ones?}.

.......................Out-Band Sync Suppression........................
Out-band gated sync systems also exist, such as in early Hamlin
converters. In this system, the reference signal is located on an
unused channel, usually towards the higher end (channels in the 40's
and 50's are common, but never in the low 30's due to potential false
signalling.) The signal is comprised of only sync pulse information
without any video. Tuning in such a channel will show nothing but a
white screen and will usually have no audio.

.............................SSAVI / ZTAC...............................
SSAVI is an acronym for Synchronization Suppression and Active Video
Inversion and is most commonly found on Zenith converters. ZTAC is an
acronym for Zenith Tiered Addressable Converter. Besides suppressing
sync pulses in gated-sync fashion, video inversion is used to yield
four scrambling modes (suppressed sync, normal video; suppressed sync,
inverted video; normal sync, inverted video; and normal sync, normal
video). The mode of scrambling can be changed as fast as once per field.
Their is no "reference signal" per-se, but the horizontal sync pulses
during the VBI are not suppressed, allowing a phased-lock loop to be
used to generate the missing sync pulses. Information on whether the
video is inverted or not is contained in the latter-half of one of the
lines of video, usually line 20 or 21. The Drawing Board column of
Radio-Electronics starting in August '92 and going through early '93
described the system and provided several circuits for use on an SSAVI
system. Audio in the system can be "scrambled" - usually by burying it
on a subcarrier that's related mathematically to the IF component of the
signal. Addressable data for Zentih systems is sent in the VBI, lines
10-13, with 26 bits of data per line.

..............................Tocom systems.............................
The Tocom system is similar to the Zenith system since it provides three
levels of addressable baseband scrambling: partial video inversion,
random dynamic sync suppression and random dynamic video inversion.
Data necessary to recover the signal is encrypted and sent during lines
17 and 18 of the VBI (along with head-end supplied teletext data for
on-screen display). The control signal contains 92 bits, and is a 53 ms
burst sent just after the color burst. Up to 32 tiers of scrambling can
be controlled from the head-end. Audio is not scrambled.

..........................New Pioneer systems...........................
The newer 6000-series converters from Pioneer supposedly offer one
of the most secure CATV scrambling technologies from a "major" CATV
equipment supplier. From the very limited information available on the
system, it appears that false keys, pseudo-keys and both in-band and
out-band signals are used in various combinations for a secure system.
From U.S. patent abstract #5,113,441 which was issued to Pioneer in
May '92 (and may or may not be used in the 6000-series converters, but
could be), "An audio signal is used on which a key signal containing
compression information and informaton concerning the position of a
vertical blanking interval is superimposed on a portion of the audio
signal corresponding to a horizontal blanking interval. In addition,
a pseudo-key signal is superimposed...so that the vertical blanking
interval cannot be detected through the detection of the audio signal...
Descrambling can be performed by detecting the vertical blanking
interval based on the information...in the key signal, and decoding
the information for the position which is transmitted in the form of
out-band data. Compression information can then be extracted from
the key signal based on the detected vertical blanking interval, and
an expansion signal for expanding the signal in the horizontal and
vertical blanking periods can be generated." {If anyone has any better
information on the 6000-series scrambling technique, please send mail!}
Note that Pioneer boxes are "booby-trapped" and opening the unit will
release a spring-mechanism which positively indicates access was gained
to the interior (and sends a signal to the head-end on a two-way system,
and may disable the box completely.) {See U.S. patent #4,149,158 for
details.} The mechanism cannot be reset without a special device.

Pioneer systems transmit their addressing data on 110.0 MHz.

.....................New Scientific-Atlanta Systems.....................
Some of the early S-A boxes used 6 dB only sync suppression (some of
the 8500 models), and some of the 8550 boxes are tri-mode systems.
The three digit number after the model (such as 321) is a code which
indicates the make of the descrambler in the unit. Apparently some of
the newer S-A boxes use a technique called "dropfield". {If anyone has
more information on any of the 85xx-series or the 8600^x boxes, or an
explanation of "dropfield", send mail...}

Scientific-Atlanta systems transmit their addressing data on 106.2 or
108.2 MHz.

............................Oak "Sigma" Systems.........................
This a secure system which replaces the horizontal sync of each line
of video with a three-byte digital word. Video is switched from
inverted to non-inverted between scene changes, and the colorburst
frequency is shifted "up". This is a standard "suppressed" sync
video scrambling method and is relatively simple to defeat with the
appropriate circuitry. HOWEVER, the three-byte digital word in the
area where the sync normally is contains audio and sync information.
The first two bytes contain a digitized versions of the audio, the
third byte contains sync information (and perhaps addressing data?) The
two bytes of digitized audio are encrypted; a separate carrier signal
contains the decryption keys for the digital audio datastream.

............................Jerrold Baseband............................
No information on techniques used by Jerrold "baseband" converters. {If
anyone has information on other Jerrold scrambling methods other than
those mentioned above, send mail.}

...............................Chameleon................................
The research and development division of Fundy Cable Ltd., NCA
Microelectronics, has a systemd dubbed "Chameleon". They claim it is
a cost-effective solution that prevents pay TV theft by digitally
encrypting the video timing information of sync suppression systems. The
company claims the technology has been proven to be effective against
pirate and tampered boxes. Supposedly, existing decoders can be upgraded
to Chameleon technology with a low-cost add-in circuit, and that the
card's sealed custom IC, developed by NCA, is copy-proof.

..............................VideoCipher...............................
The VideoCipher system is now owned by General Instrument and is used
primarily for satellite signals at this time. VideoCipher I is the
"commercial" version which uses DES (Data Encryption Standard)-encrypted
audio AND video. A VCI descrambler is not available for "home" owners.
VideoCipher II is the now-obsolete system which used a relatively simple
video encryption method with DES-encrypted audio. (Specifically, the
audio is 15 bit PCM, sampled at ~44.1 KHz. It is mu-law companded to
10 bits before transmission.) This has recently been replaced by the
VideoCipher II+, which has been incorporated as the 'default' encryption
method used by VideoCipher IIRS (a smart-card based, upgradeable
system). Supposedly, coded data relating to the digitized, encrypted
audio is sent in the area normally occupied by the horizontal sync
pulse in the VCII system. (The Oak Sigma CATV system uses a similar
technology.) Several methods existed for pirating the VCII based system,
and some SUPPOSEDLY exist for the new VCII+ format, although this has
never been verified. See the rec.video.satellite FAQ list for more
information.

.........................DigiCable/DigiCipher...........................
DigiCipher is an "upcoming" technology being developed by General
Instrument for use in both NTSC and HDTV environments. The DigiCipher
format is for use on satellites, and the DigiCable variation will
address CATV needs. It provides compression algorithms with forward
error correction modulation techniques to allow up to 10 "entertainment
quality" NTSC channels in the space normally occupied by one channel.
It provides true video encryption (as opposed to the VCII-series which
only DES encrypts the audio). In a Multiple Channel Per Carrier (MCPC)
application, the data rate is ~27 MB/second via offset QPSK modulation.
Audio is CD-quality through Dolby AC-2 technology, allowing up to four
audio channels per video channel. The system uses renewable security
cards (like the VCIIRS), has 256 bits of "tier" information, copy
protection capability to prevent events from being recorded, commercial
insertion capability for CATV companies, and more. The multichannel NTSC
satellite version of DigiCipher started testing in July of 1992, and
went into production several months later.

................................B-MAC...................................
MAC is an acronym for Mixed Analog Components. It refers to placing TV
sound into the horizontal-blanking interval, and then separating the
color and luminance portions of the picture signal for periods of 20
to 40 microseconds each. In the process, luminance and chrominance are
compressed during transmission and expanded during reception, enlarging
their bandwidths considerably. Transmitted as FM, this system, when used
in satellite transmission, provides considerably better TV definition
and resoluton. Its present parameters are within the existing NTSC
format, but is mostly used in Europe at this time. {Does anyone know
if the D2-MAC system is just a variation of this, or is it completely
different? What's new in the D2-MAC system?}

________________________Miscellaneous_Information_______________________

.........................Two-Piece vs. One-Piece........................
There are both advantages and disadvantages to the one-piece and
two-piece descramblers often advertised in the back of electronics
magazines. The "one-piece units" are real cable converters, just
like you'd get if you rented one from the cable company. It has the
advantages of "real" descrambling circuitry and the ability to "fit-in"
well when neighbors come over (avoids those "my box doesn't look like
that...or get all these channels!" conversations :-) A disadvantage is
that if you move or the cable company installs new hardware, you may now
have a worthless box -- most one-piece units only work on the specific
system they were designed for. Another disadvantage is that if the box
has not been modified, it can be very easy for the head-end to disable
the unit completely. (See Market Codes & Bullets, below.)

A "two-piece unit" ("combo") usually consists of an any-brand cable TV
tuner with a third-party "descrambler" (often referred to as a "pan")
which is designed to work with a specific scrambling technology. The
descrambler typically connects to the channel 3 output of the tuner,
and has a channel 3 output which connects to your TV. (Although some
tuners have a "decoder loop" for such devices.) They have the advantage
that if you move or your system is upgraded, you can try to purchase a
new descrambler -- which is much cheaper than a whole new set-up. You
also can select the cable TV tuner with the features you want (remote,
volume control, parental lockout, baseband video output, etc.) Two-piece
units typically cannot be disabled by the data stream on your cable.
(Note however that there ARE add-on "pans" manufactured by the same
companies who make the one-piece units that DO pay attention to the data
stream and can be disabled similarly!) The main disadvantage is that a
third-party descrambler MAY not provide as high of quality descrambling
as "the real thing", and it may arrouse "suspicion" if someone notices
your "cable thing" is different from theirs.
 
........................Jerrold Numbering System........................ 
To decode older Jerrold converters, the following chart may be helpful.
(Note that some spaces may be blank.) {Send along any additions or other
numbering systems you know of!}

 __ __ __ __ - __ __ __
 |  |  |  |    |  |  |
 |  |  |  |    |  |  |___ T = two-way capability, C = PROM programmable
 |  |  |  |    |  |
 |  |  |  |    |  |______ DI = Inband decoder, DO = Outband decoder,  
 |  |  |  |    |          PC = Single pay channel, A = Addressable
 |  |  |  |    |
 |  |  |  |    |_________ Output channel number (3 very common)
 |  |  |  |    
 |  |  |  |______________ D or I = tri-mode system, N = parental lockout   
 |  |  |                    feature (6 dB-only systems are "blank" here)
 |  |  |
 |  |  |_________________ M = mid-band only, X = thru 400 MHz,
 |  |                     Z = thru 450 MHz, BB = baseband
 |  |   
 |  |____________________ S = Set-top, R = Remote
 | 
 |_______________________ D = Digital tuning, J = Analog tuning

Also note that some Jerrold converters (particularly the DP5 series
and maybe others) have a tamper-switch, and that opening the box will
clear the contents of a RAM chip in the converter. This may or may not
be corrected by letting the unit get "refreshed" by the head-end data
stream.

Most Jerrold systems transmit their addressing data near 106.5 MHz.

................Scientific-Atlanta Suppressed Sync Boxes................
Model 8600 - _ _ _ _
             | | | |
             | | | |___ Impulse PPV Return: N=none, T=telephone, R=RF
             | | |_____ Dual cable option: N=none, D=dual cable
             | |_______ Descrambler type: S=SA standard, K=oak
             |_________ Channel: S=selectable channel 3/4
   The 8600 has 240 character on-screen display, multimode scrambling, 
   8 event 14 day timer, and is "expandable"...

Model 859_ - 7 _ 7 _
         |     |   |
         |     |   |__ Dual cable option: D=dual cable
         |     |______ Descrambler: 5=SA scrambling+video inversion,
         |                          7=5+Oak
         |____________ 0=No Impulse PPV, 5=Telephone IPPV, 7=RF IPPV
   The 8590s feature volume control, multimode scrambling, 8 event
   14 day timer...

Model 858_ - _ 3 _ - _ 
         |   |   |   |__ Dual cable option: D=dual cable
         |   |   |______ Data carrier: 6=106.2 MHz, 8=108.2 MHz
         |   |__________ Channel: 3=channel 3, 4=channel 4
         |______________ 0=No Impulse PPV, 5=Telephone IPPV, 7=RF IPPV
   The 8580s use dynamic sync suppression, 8 event 14 day timer, and
   built-in pre-amp.

The 8570 is similar to the 8580.

Model 8550 - _ _ _
             | | |__ 1=108.2 MHz data stream
             | |____ Jerrold, dropfield, SA descrambling
             |______ Channel: 3=channel 3
   The 8550 is not a current model; it can be replaced with an 8580-321.

Non-addressable products include the 8511, 8536, and 8540.

{If anyone has more details/corrections, please send them along.}

.............................Market Codes...............................
Note that almost every addressable decoder in use today has a unique
"serial number" programmed into the unit -- either in a PROM,
non-volatile RAM, EAROM, etc. This allows the head-end to send commands
specifically to a certain unit (to authorize a pay-per-view events, for
example.) Part of this "serial number" is what is commonly called a
"market code", which can be used to uniquely identify a certain cable
company. This prevents an addressable decoder destined for use in
Chicago from being used in Houston. In most cases, when a box receives a
signal with a different market code, it will enter an "error mode" and
become unusable. This is just a friendly little note to anyone who might
consider purchasing a unit from the back of a magazine -- if the unit
has not been "modified" in any way to prevent such behavior, you could
end up with an expensive paper weight... (see next section)

.............................Test Chips.................................
So-called "test chips" are used to place single-piece converters (that
is, units with both a tuner and a descrambler) into full service. There
are a number of ways to accomplish this, but in most cases, the serial
number/market code for the unit is set to a known "universal" case (RARE
THESE DAYS) or, better yet, the comparison checks to determine which
channels to enable/disable are bypassed by replacing an IC in the unit.
Hence, the "descrambler" will always be active, no matter what. This
latter type of chip is superior because it cannot be disabled and is
said to be "bullet proof", even if the cable company finds out about a
"universal" serial number. (When the cable company finds out about a
universal serial number, it is easy for them to disable the converter
with a variation on the "bullet" described below.)

................................Cubes...................................
A relatively new "test device" has been advertised in magazines such
as Electronics Now (formerly Radio-Electronics) and Nuts & Volts.
It's called a "cube" and it SIMULATES the addressing data signal for
a cable box. You plug the cable into one side, where it filters out
the real data signal, and out the other side comes a normal signal,
with a new data stream. This new data signal tells whatever boxes are
connected after it to go into "full-service" mode (including any cable
company-provided boxes). It is usually a non-destructive signal, and if
the the "cube" is removed from the line, the real data signal gets sent
to the converter which then goes back to normal operating mode. I say
"usually non-destructive" because there are some cubes that re-program
the electronic serial number in a box to a new value. (This has the
advantage that it will work with ANY converter the unit was designed
for.) The "non-destructive" versions of the "cube" usually require
that you provide the serial number from the bottom of the converter
you're interested in "testing". That way a custom IC can be programmed
to address that converter with the necessary codes. (Otherwise the
converter would ignore the information, since the serial number the cube
was sending and the one in converter wouldn't match.)

...............................Bullets..................................
First and foremost, THE "BULLET" IS NOTHING MORE THAN THE NORMAL CABLE
DATA STREAM WITH THE APPROPRIATE "CODE" TO DISABLE A CONVERTER WHICH
HAS NOT BEEN ACKNOWLEDGED BY THE CABLE COMPANY. For instance, the head
end could send a code to all converters which says "unless you've been
told otherwise in the last 12 hours, shut down." All legitimate boxes
were individually sent a code to ignore this shut down code, but the
pirate decoders didn't get such a code because the cable company doesn't
have their serial number. So they shut down when the see the "bullet"
code. The "bullet" is NOT a harmful high-voltage signal or something as
the cable companies would like you to believe -- if it was, it would
damage anyone with a cable-ready TV or VCR connected to the cable (not
something the cable company wants to deal with!) The only way to get
"caught" by such a signal is to contact the cable company and tell them
your illegal descrambler just quit working for some reason. :-) Not a
smart thing to do, but you'd be surprised (especially if it's someone
else in the house who calls, like a spouse, child, babysitter, etc.)
While we're on the subject, it's also not a good idea to have cable
service personnel come into your residence and find an unauthorized
decoder. If you have one, use common sense and tell anyone you live with
to call YOU and NOT the cable company if something goes wrong. Just some
friendly advice...

.............Time Domain Reflectometry / Leak Detection.................
The cable company can use a technique called "Time Domain Reflectometry"
(TDR) to try and determine how many devices are connected to your cable.
In simple terms, a tiny, short test signal is sent into your residence
and the time domain reflectometer determines the number of connections
by the various "echoes" returned down the cable (since each device
is at a different point along the cable, they can be counted.) Each
splitter, filter, etc. will affect this count. A simple way to avoid
being "probed" is to install an amplifier just inside your premises
before any connections. This isolates the other side of the cable from
the outside, and a TDR will only show one connection (the amplifier).

The cable company also has various ways of detecting signal "leaks"
in their cable. The FCC REQUIRES them to allow only so much signal to
be radiated from their cables. You may see a suspicious looking van
driving around your neighborhood with odd-looking antennas on the roof.
These are connected inside to field strength meters which help locate
where the leaks are coming from so they can be fixed (to prevent a
fine from the FCC!) If you've tampered with a connection at the pole
(say, to hook up a cable that had been disconnected) and didn't do a
good job, chances are the connection will "leak" and be easily found by
such a device. This can also happen INSIDE your residence if you use
cheap splitters/amplifiers or have poorly-shielded connections. The
cable company will ask to come inside, and bring with them a portable
field strength meter to help them locate the problem. Often they will
totally remove anything causing the leak, and may go further (e.g.,
legal action) if they feel you're in violation of your contract with
them (which you agree to by paying your bill.) Obviously it's a bad
idea to let cable service personnel into your house if you ARE doing
something you shouldn't (which you shouldn't be in the first place), but
if you DON'T let them in (as is your right), it will definitely arouse
suspicion. Eventually you will have to let them in to fix the "leak", or
they will disconnect your cable to stop the leak altogether. (After all,
it's a service, not a right, to receive cable!)

...................Some Common Ways Pirates Get Caught..................
There are many ways for a "pirate" to get caught. Since stealing cable
is illegal in the U.S., you can be fined and sent to jail for theft of
service. Cable companies claim to lose millions of dollars in revenue
every year because of pirates, so they are serious in their pursuit of
ridding them from their system.

First, a pirate will often show-off the fact they can get every channel
to their friends. Pretty soon lots of people know about it, and then the
cable company offers a "Turn In A Pirate And Get $100" program. A friend
needs the money and turns the pirate in. Busted.

Second, a pirate (or unsuspecting housemate of a pirate who knows
nothing about whats going on) calls the cable company to report a
problem with the equipment or signal. The cable company makes a service
call and finds illegal equipment connected to the cable. Busted.

Third, during a pay-per-view event such as a fight, the cable company
offers a free T-shirt to all viewers. Little does the pirate know that
just before that message appeared on the screen, legitimate viewer's
boxes were told to switch to another channel WHILE STILL DISPLAYING
THE ORIGINAL CHANNEL NUMBER (yes, cable boxes can do this.) So now the
legitimate subscriber continues to see the "original" signal (without
the T-shirt offer), while the pirate gets an 800 number plastered on
the screen. The pirate calls, and the cable company gets a list of all
pirates. Busted.

Fourth, a big cable descrambler business gets busted. The authorities
confiscate their UPS shipping records and now have a list of "customers"
who most likely ordered descramblers for illegitimate use. Busted.

And this is only the beginning. Unconfirmed reports of the cable company
driving around with special equipment allowing them to determine what
you're watching on your TV (like HBO, which you don't pay for) have also
been mentioned.

........................The Universal Descrambler.......................
In May of 1990, Radio-Electronics magazine published an article on
building a "universal descrambler" for decoding scrambled TV signals.
There has been much talk on the net about the device, and many have
found it to be lacking in a number of respects. Several modifications,
hoping to fix some of the problems have also been posted, with limited
success. The Universal Descrambler relies on the presence of the
colorburst for its reference signal. In a normal line of NTSC video,
the colorburst is 8 to 11 cycles of a 3.579545 MHz clock (that comes
out to 2.31 microseconds) which follows the 4.71 microsecond horizontal
sync during the horizontal blanking interval. {Whew!} Since a large
number of scrambling systems depend on messing with the horizontal sync
pulse to scramble the picture, the Universal Descrambler attempts to
use the colorburst signal to help it replace the tainted sync pulse.
Unfortunately, random video inversion is still a problem, as are color
shifts which occur from distorted or clamped colorburst signals, etc.
Most people have not had very good results from the system, even after
incorporating some modifications.

________________________Glossary_of_Related_Terms_______________________
{Suggestions or contributions to the glossary are welcome!}

CATV:	Acronym for Community Antenna TeleVision. Originally cable TV 
        came about as a way to avoid having everyone in a community have
        to spend a lot of money on a fancy antenna just to get good TV
        reception.  Really all you need is one very good antenna and 
	then just feed the output to everyone.  It was called Community
        Antenna Television (CATV).  Of course, it has grown quite a bit
        since then and everyone now just calls it cable TV.  The old
        acronym still sort-of works. 
Converter:
	A device, sometimes issued by the cable company, to "convert"
	many TV channels to one specific channel (usually channel 3).  
	Used early-on when VHF & UHF channels were on different dials
	(and before remote controls) to provide "convenience" to cable
	customers.  Now mostly considered a nuisance, thanks to the
	advent of cable-ready video equipment, they are mainly used as
	descramblers.
	An "addresable" converter is one that has a unique serial number
	and can be told (individually) by the head-end to act in a
	certain manner (such as enabling channel x, but not channel y). 
	Addressable converters nearly always contain descramblers for
	decoding premium services subscribed to by the customer. 
Colorburst:
	Approximately 8 to 10 cycles of a 3.579545 MHz clock sent during
	the HBI.  This signal is used as a reference to determine both 
	hue and saturation of the colors.  A separate colorburst signal 
	is sent for each line of video, and are all exactly in phase (to 
	prevent color shifts). 
Control Signal:
	The first 11.1 microseconds of a line of NTSC video.  The signal
	area from 0 to 0.3 volts (-40 to 0 IRE units) is reserved for
	control signals, the rest for picture information.  If the
	signal is at 0.3 volts (or 0 IRE) the picture will be black. 
	See IRE Units; Set-up Level. 
Field:	One half of a full video frame.  The first field contains
	the odd numbered lines, the second field contains the even
	numbered lines.  Each field takes 1/60th of a second to
	transmit.  Note that both fields contain a complete
	vertical-blanking interval and they both (should) have the same
	information during that interval.  Since the NTSC standard is
	525 lines, each field contains 262.5 lines--therefore it's the
	half-line that allows the two fields of a frame to be
	distinguished from one another.  See Frame; Line. 
Frame:	An NTSC video signal which contains both fields.  A frame
	lasts 1/30th of a second.  See Field; Line. 
Head-end:
	The main cable distribution facility where your CATV signal
	originates from.  (Easily identifed by several large satellite
	dishes, some smaller ones, and usually an antenna tower.)
HBI:	Acronym for Horizontal Blanking Interval.  The first 11.1
	microseconds of a line of video.  It contains the front porch,
	the 4.71 microsecond horizontal sync pulse, the 2.31
	microseconds of colorburst, and the back porch.  The horizontal
	sync pulse directs the beam back to left side of the screen.
	Almost every scrambling method in use today mutataes this part
	of the signal in some way to prevent unauthorized viewing.  See
	Colorburst.
Interlace:
	Term used to describe the dual-field approach used in the NTSC
	standard.  By drawing every other line, screen flicker is
	increased--but if all the lines were painted sequentially, the 
        top would begin to fade before the screen was completely "painted". 
        (Computer monitors, which do "paint" from top to bottom, do not
        have the problem due to higher refresh rates.)
IPPV:	Impulse Pay-Per-View.  A method whereby a viewer can order a 
	pay-per-view event "on impulse" by just pushing an "Order" (or
        similar) button on a remote control or cable converter keypad.
        A customer's purchases are sent back to the head-end via a
	standard telephone connection (the converter dials into the cable
	co. computer and uploads the data) or via radio frequency (RF) if 
	the cable supports two-way communication (most don't).  A pre-set
	maximum number of events can be ordered before the box requires 
	the data to be sent to the head-end for billing purposes.
IRE Units:
	IRE is an acronym for Institure of Radio Engineers.  The NTSC
	standard calls for a peak-to-peak signal voltage of 1 volt. 
	Instead of referring to the video level in volts, IRE units are
	used instead.  The IRE scale divides the 1- volt range into 140
	parts, with zero-IRE corresponding to about 0.3V.  The full
	scale goes from -40 IRE to +100 IRE.  This is convenient scale
	to make a distinction between control signals (< 0 IRE) and
	picture signals (> 0 IRE).  See Control Signal. 
Line:	A video signal is a series of repeated horizontal lines,
	consisting of control and picture information.  The color NTSC
	standard allows a total time of 63.56 microseconds for each
	line, and each frame is composed of 525 lines of video
	information.  The first 11.1 microseconds make up the horizontal
	blanking interval, or control signal, the following 52.46 
	microseconds make up the picture signal.  See HBI; VBI.
NTSC:	Acronym for National Television Standards Committee (or
	Never The Same Color, if you prefer :-) 
Picture Signal:
	The 52.46 microseconds of signal following the control signal. 
	Information in this area is between 0 and 100 IRE units.  See
	IRE Units. 
PPV:	Acronym for Pay-Per-View.  A revenue-enhancing system where 
	customer's pay to watch a movie or event on a "per view" basis.
	Cusomers usually place a phone call to a special number and order
	the event of their choice; some systems provide Impulse PPV.
	The presence of a PPV movie channel or your system guarantees
	you have addressable converters.  See IPPV.
Set-up Level:
	Picture information technically has slightly less than 100 IRE
	units available.  That's because picture information starts at
	7.5 IRE units rather than at 0 IRE units.  The area from 0 to
	7.5 IRE units are reserved for what is commonly called the
	"set-up level".  Having a small buffer area between the control
	signal information and the picture information is a "fudge
	factor" to compensate for the fact that real-life things that
	don't always work as nicely as they do on paper. :-)  See IRE
	Units. 
VBI:	Acronym for Vertical-Blanking Interval.  The first 26 lines of
	an NTSC video signal.  This signal is used to direct the beam
	back to the upper-left corner of the screen to start the next
	frame.  In order for the horizontal sync to continue operating,
	the vertical pulse is serrated into small segments which keep
	the horizontal circuits active.  Both actions can then take
	place simultaneously.  The VBI is the most common place for 
	"extra" information to be sent, such as various test signals, 
	and in some cable systems, a data stream.

______________________End_of_rec.video.cable-tv_FYI_____________________

