Pointers to info on how XM and Sirius systems work, specifically as
regards authorization?
When a satellite authorizes a given radio, does it do it by sending
that radio (and, as a side effect, all other radios) some kind of
digital key that combines with some unique built-in matching key in
that particular radio to enable it to decode the broadcast content?
If so, presumably if you stop paying your bill it can also deauthorize
your radio by sending something to wipe out the code?
But suppose you put your radio in a shielded box, stop paying, wait a
few months until they give up trying to deauthorize you, then bring it
back out -- are you still authorized? Or does every authorized radio
have to get reauthorized at some periodic interval?
Bottom line: Do individual radios actually talk back to the satellites
at any point? Or do authorization and other command signals flow only
from the satellites to the radio?
(Not looking to play any games here -- just interested to understand
how it works.)
[TELECOM Digest Editor's Note: An interesting problem, and one that
the gas company deals with a lot in older inner city areas, which is
gradually getting cured. Many years ago, gas was delivered in underground
pipes (it still is), but as a matter of economics the gas company used
a lot of 'branch lines' off the main feed. For example, there are two
dwellings on a piece of land, one sort of behind the other one. Gas
company runs a pipe which attaches to one meter, then the pipe
'branches' off and runs to the second meter. First meter owner gets
delinquent in paying his gas bill, and refuses to allow access to his
basement for the purpose of cutting off his service. Gas company keeps
telling the man "let us in your basement so we can lock off your
meter." Man refuses to do so, assuming there is no way for gas company
to cut his service if they can't get in his basement. What the gas
company will do is get a permit from the city to excavate in the street
and cut him off at that point. The only trouble is, the person on the
other end of the property, with his own meter, which is in good standing,
winds up getting cut also.
Needless to say, that man (second meter) raises plenty of hell, and
demands his gas service back. Gas company claims it was an accident,
and they will turn him back on ASAP, but there is one big problem with
natural gas which does not apply with other utilities; before they can
turn him back on (with the consequential lighting of his pilot lights
to prevent explosions, etc, now they *absolutely must* get the other
guy's pilot light relighted as well (or in actual practice cut his
meter) to avoid possible explosions at that end. So they turn one
neighbor against the other one, telling second meter, "Gee, we would
love to restore *your* service but we can't get into first meter and
under the law, even if we should not have 'accidentally' cut off your
service, we have to light his pilot as well (and all the other
pilot lights on the same branch line)." You better believe second meter
finds first meter (if he has to break the basement door down himself)
and imposes on him to allow the meter to be cut off so that then gas
company can turn the line back on, and go around lighting all the
pilot lights for all the other residents on the 'branch line'.
Western Union also had similar woes with their clock service fifty or
more years ago: a large office building, maybe there were a few
dozen clocks on the circuit. Some joker would not pay his clock bill
and assume WUTCO can't do anything about it if I don't let them in the
office to remove the clock. Their policy was where an individual clock
was on an individual circuit, WUTCO would put a 'load' on the line
and just leave it there. Eventually the load would overcome the
tension from the escapement spring and stop the pendulum from swinging,
which had the effect of denying any more clock service. When the guy
paid up, the clock man came back out and restarted the clock. But if
(as was common) there were fifty clocks and only one setting-circuit
handling them all; one joker does not pay and refuses to give up the
clock; WUTCO had to shut them all down, then once they were all dead
(due to the load on the line), go back and restart the 49 good customers
and let the one bad guy sit there and stew in his juices.
Of course there are no clocks with WUTCO works in them any longer, and
although gas company still now and then has to resort to cutting off
many customers temporarily (and use *them* as tools to get after the
bad guy) and delinquencies in paying for gas is more common these days
for various economic reasons, gas company is gradually redoing their
outside plant infrastructure, so that everyone gets their own direct
feed to the gas main, so customers either voluntarily admit the gas
man to inspect/lock out their meter for non-payment, or gas company
excavates in the street as needed, but now there are no innocent
victims in the process, or not as many as in the past.
My understanding is satellite receiving units do not 'talk back' to
the satellite; everything is done from the satellite end, and as long
as there is any 'unfinished business' with any one receiver, the
satellite company just keeps on sending over and over the required
codes. DISH has those little plastic 'smart cards' which have to
be replaced once a year or so, so I assume if you were not paying, at
best, you'd get the remainder of the time available before the Smart
Card ran out. I do not know what some of the others are doing. PAT]
AES (siegman@stanford.edu)