698 lines
40 KiB
Plaintext
698 lines
40 KiB
Plaintext
From news.dorsai.org !news.sprintlink.net!uunet!cs.utexas.edu!sdd.hp.com!hp-cv!hp-pcd!hp-vcd!egurney Sat Jan 8 23:41:59 1994
|
|
Newsgroups: rec.video.cable-tv
|
|
Path: news.dorsai.org !news.sprintlink.net!uunet!cs.utexas.edu!sdd.hp.com!hp-cv!hp-pcd!hp-vcd!egurney
|
|
From: egurney@vcd.hp.com (Eddy J. Gurney)
|
|
Subject: FAQ: rec.video.cable-tv FYI List (09/21/93)
|
|
Sender: news@vcd.hp.com (News user)
|
|
Message-ID: <CJ49x3.F5r@vcd.hp.com>
|
|
Date: Tue, 4 Jan 1994 17:58:15 GMT
|
|
Expires: Thu, 3 Feb 1994 17:58:15 GMT
|
|
Nntp-Posting-Host: hpvcleg.vcd.hp.com
|
|
Organization: Hewlett-Packard VCD
|
|
X-Newsreader: TIN [version 1.2 PL1.4]
|
|
Lines: 682
|
|
|
|
--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_____________________
|
|
|