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HOW JERROLD(tm) ADDRESSING WORKS

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magicboxes

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Jan 20, 1998, 3:00:00 AM1/20/98
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We have had tons of e-mails from people wanting to know how Jerrold(tm)
addressing works and why some testers they buy corrupt their box. (Even
after the dealer tells them it won't)

Well, here it is:


FAQ - Jerrold(tm) Addressing January 17,1998
magicboxes.com

CONTENTS
1) How does the cable company control a Jerrold Descrambler?
2) What is the difference between a CFT22xx and the other models?
3) When is the "ESN" or serial number used?
4) Why did the T2,RFT series boxes fail on CFT22xx?
5) How can I fix my box once I used a T2,T2A,RFT tester on by rented
descrambler?
6) What is multi-mode REALLY?
7) What is the solution to SERIAL NUMBERS THEN?

SECTION-1.
1) How does the cable company control a Jerrold Descrambler?


The cable company sends a series of commands to your Jerrold box through
an FM frequency. (Generally 89.3,97.5,106.5,108.5,122.7Mhz). The command
syntax is:

(length 1byte) (command type 1 byte) (command 1 byte) (paramaters ... many
bytes) (checksum .. 1 byte)


Everyones cable box has a serial number on it. (Written on the bottom). It
is 5 bytes in length and usually begins with 2.
Inside your CFT/DPBB is a subscriber number. The subscriber number is from
0 to approx 225,000. Inside your box is also a site code which is used by
the cable company to identify which *cable company* the box is to work in.

Put very easily,

Inside you have:

A Serial Number --- On outside of box
A Dynamic Subscriber Number --- a number programmed in you box by the cable
company (no one knows it)
A Site Code --- Every cable company has their own number


SERIAL NUMBER: This number is only inside the box in case it gets
*confused*. It is a static number which never changes. This means if you
called the cable company and said you had a problem like "You converter is
disconnected". then they would address your box using the serial number.
There are very few commands which use the serial number and they only ever
change data inside the box like: Dynamic Subscriber Number, Site Code,
etc...

DYNAMIC SUBSCRIBER NUMBER: This number is used for most (really all)
standard operating commands. Commands that would use the DSN would be:

Channel Map Changes
Program Authorizations
Two-Way communications
Time, data.
Shutdowns, and reset timer commands.

SITE CODE: Is used in most commands to ensure the only boxes using those
commands are the boxes programmed for that area. Ie: Lets say you took your
Jerrold(tm) box from your state and brought it into another state using the
same kind of technology. Chances are the subscriber number in your box
could be the same as someones in the area you just hooked your box into. In
order to stop that kind of movement Jerrold implimented a site code. If the
site code coming down the line inside the commands don't match your box
then your box will actually shut down (E8)... RFT-Plus,T2s caused this..
(but we will get to that later)


Types of commands (and we will even get into some actual codes):

RESET TIMER Syntax: Length =6 Type=249 DSN (dynamic subscriber number)
(checksum)

The reset timer command resets an internal timer in your Jerrold box. Why?
Well, GI thought that if some subscriber got smart and blocked the FM data
from getting through the cable company would no longer be able to address
the box. Right? Wrong - GI made sure that if your box doesn't hear a reset
timer (with its own unique DSN) then its time to shutdown. (Error 1).

CHANNEL MAP UPDATE.

This command controls what channels are where. This command requires a DSN.
Each command can move 8 channels around.

SHUTDOWN BOX Syntax: Length =6 Type=248 DSN (dynamic subscriber number)
(checksum)

This command is sent to ALL the DSNs the cable company currently does not
use AND as well uses it on all subscribers which don't pay their bill,
steal their box, etc... This command puts the famous "YOUR CONVERTER IS
DISCONNECTED. PLEASE CONTACT YOUR CABLE OPERATOR"

TURN ON CHANNELS (Global) Syntax: Length=4 Type=253 Command=127/129
ChannelId (1byte) (Checksum)

This command turns channels on/off (premium/pay per view). It does not
require a DSN and makes many boxes very happy :)


SET DYNAMIC SUBSCRIBER NUMBER Syntax: Length=16 Type=253 Command=95
(serial# 5 bytes) (ID - usually 224 191 127 62) (Site code (4bytes))
(Checksum)

This command is issued by the Cable company when there is a problem
addressing your box. It resets your DSN and Site code to the numbers
passed. (The RFT/T2 units use this command on CFT22xx units,,, and boy o
boy does it cause hell in your set top!)


There are many other commands ... The above should give you the idea.

SECTION-2
2) What is the difference between a CFT22xx and the other models?


The CFT22xx model units were put out because GI was fed up with simple
cubes turning on all the channels in their boxes. They took out ALL global
commands in the CFT22xx units. (That means you must address the unit by its
DSN ONLY!).

This caused serious problems for the cubes out there - the only way to make
one work is to actually CHANGE the subscriber information in the box. This
will work for a little while but the cable company knows the box has been
tampered with. (In fact, the only way to get your old DSN back in is to
call the cable company and ASK them to reboot your unit for some silly
reason. (Cable companies aren't doing that too often anymore).)

Any CUBE/T2/RFT/TESTER that requires you to enter a serial number WILL
DEFINATELY CHANGE YOUR DSN. In fact, Old T2s and RFT-Plus, RFT-Gold even
change your site code. You know what that means now --- shut off the tester
and your set-top is "Out of the AREA"-Error 8 - "YOUR CONVERTER IS
DISCONNECTED"...

SECTION-3
3) When is the "ESN" or serial number used?

The ESN - Serial number is ONLY EVER used to CHANGE subscriber numbers and
SITE CODES. THE SERIAL NUMBER DOES NOT TEST CHANNELS.


SECTION-4
4) Why did the T2,RFT series boxes fail on CFT22xx?

When you plug in a T2/RFT (or ANY other requiring you to enter the SERIAL
number on your box (Either by an F2 or barcode)) and enter the serial
number, the cube WILL change important addressing information used by the
cable company to address/talk to your box. If your in a two way system you
have REAL problems... If your box doesn't respond to their commands they
have only two possibilities to investigate:

1) An unplugged box (don't worry , they will try day after day for a month)
2) Your box information has been changed by a cube.

How can they tell?

Easy --- If your using an old T2/RFT they just have to see the error number
in your box (E8 - Invalid Site Code) or if its the *new* line of
"Uncorruptable T2 testers" then all they have to do it SHUTDOWN the DSN the
T2 puts out for ALL devices. When you call for help- your busted!

EASY AGAIN: T2s and RFTs do NOT transmit ONLY towards your cable box. They
transmit down to the pole OUTSIDE your house. (try it... In/Out ... it
makes no difference which way you hook them up). If your box is not
responding they can very quickly disconnect your cable and listen for YOUR
CUBE... Bad news when they record the data coming out of your LIVING ROOM!


SECTION-5
5) How can I fix my box once I used a T2,T2A,RFT tester on by rented
descrambler?


If your lucky you can call the cable company for a re-boot. If you have
two-way they WILL show up at your door. If you call the cable company too
often for REBOOTs they will investigate. They can HEAR your cube on your
cable line outside your house if they feel there is a problem - AUTOBUST
(They do not EVEN have too call you if they feel there is a problem - just
check it out).


SECTION-6
6) What is multi-mode REALLY?

Multimode is a command sent out by the cable company (global command) which
tells your box that the scrambling system is about to change. If your box
doesn't hear the command it will descramble the wrong way. This generally
makes the picture unviewable. This command can be sent very often. Cubes
like the T2/RFT stop sending information every 6 seconds and allow 5
seconds of data to pass through (hoping a multi-mode command gets through).


SECTION-7
7) What is the solution to SERIAL NUMBERS/CFT 22xx THEN?


Buy a tester which supports ALL Jerrold(tm) products without having to
enter a serial number.
There are other addressing schemes used which will allow you to address
your box(CFT22xx) WITHOUT entering a serial number. Cubes like the
T2,RFT,RFT-PLUS,T2-A,RFT-???,Testbench 2200 all require the entry of a
serial number. As a consumer, find dealers who sell cubes for
CFT22xx/multimode which DONT require a serial number to be entered.

In the above document - Jerrold was used only to identify General
Instruments(Next Levels) product. Jerrold (TM) is owned by GI.

----------------------------------------------------------------------------
-------
Manufacturing and R&D in cable television descrambler technology
"We never have, and never will sell a test device requiring the user to
enter a SERIAL NUMBER"
Jim
http://www.magicboxes.com
magic...@magicboxes.com


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