If you read what it says below the logo's, in places where they haveSpehro said:Just because they've got FB and Twit logos doesn't mean they're live
streaming your mug over the internet from their security cameras.
Those companies probably just want you to tweet about them and "like"
them on FB, since "social media" is supposed to be the big thing.
Just about every retail establishment has security cameras- mostly to
watch for robberies by outside and inside perps.
Hey, are you affected by all that H2O out there? Looks real bad from
what I've seen. 8-(
Best regards,
Spehro Pefhany
If they want me, they can come and get me. I have nothing to hide andJim said:A better response...
Just because you're paranoid doesn't mean they're _not_ out to get you
;-)
...Jim Thompson
But once in a while you get a fresh rat.Jim said:I don't eat at fast food restaurants. I don't care for the rat juice
seasonings >:-}
...Jim Thompson
The problem is 1MHz is nominal. This requires a PLL using a vcxo. That
design is everywhere. Colorburst lock for example. Actually locking to
the colorburst is a harder problem.
Even very precise telco schemes use justification bits to account for
frequency difference.
Well, once the local oscillator matches the external frequency, it wont
make sense to change that frequency. Once lock occurs, then I want to
be able to compare the phase of the two waveforms. Wont a phase
comparator work if the the inputs are the same frequency but out of
phase by some amount?
You are being excessively stringent. If the phase-locked loop is fast
enough to track the planned-for phase excursions, it can track larger phase > > excursions than +/-pi radians (or +/-180 degrees if you aren't a
physicist).
You need to have some mechanism to keep track of the more-than-one-cycle
phase excursions, but that's what counters are for.
Floyd M. Gardners's book "Phaselock techniques" talks about this at length, > > and what sort of tracking errors various order of phase-locked loop can be > > expected to show.
That is an interesting assertion. I happen to have read various T-1,
T-3,
and SONET standards and they do not do that at all.
If you read what it says below the logo's, in places where they have
camera's, it clearly state's that all video taken is the property of
FB and Twitter.
There are 2 restaurants that know of here with this very same logo
and disclaimer on their door for you to read as you walk in. Most people
don't bother, their stomach are more important. But if you enjoy being
watched so be it.
Some people are so naive.
Jamie
Spehro Pefhany said:Okay, that I would not like. If you happen to have a photo of the
disclaimer I'd be interested.
Sure, provided that what the OP is trying to do is measure absolute
phase, which I don't think is the case--AFAICT he wants to do PM
demodulation.
And of course that trick runs into major difficulties if the phase is
jittering back and forth across the +-pi discontinuity, because you can
easily lose count while the loop is misbehaving. Nulling methods are
generally better for large excursions, because you never lose track of
where you are.
The phase SAR
approach that I mentioned earlier worked well because the
phase was known to be stable during the measurement--it was a scanning
heterodyne-interferometric microscope that was scanned in steps using an
acousto-optic deflector. The parlour trick there was that there was a
huge acoustic delay that showed up as this massive phase slope on the
data. Fortunately it really was a pure time delay, so after unwrapping
all it needed was a constant phase slope subtracted.
Based on his posts from some months ago, he appears to be trying to do
it over the air, in the presence of atmospheric variations. The
question is how large these are, and how fast.
Successive approximation register, see my earlier post.
You know, Bill, sometimes people talk about stuff because it's
interesting, not because they're showing off. This is a *discussion
group*, you see.
When you read the SONET standard, did you notice the part about pointer
movements?
Their role is to account for the frequency differences between network
clocks. It is possible (but not usual) to pass data through a SONET
network with a clock that is not locked to the network reference, by
means of pointer movements.
There is not such thing as 'absolute phase' in the universe.
Phase locked loop example, the error voltage is proportional to the phase CHANGES, how fast changes you can detect is set by the loop filter:
instantaneous
phase error output
^
|
|
signal 1MHz ------>-------- phase comparator ----->----loop filter ------->------ VCO (= voltage controlled oscillator) ----
| |
^ |
| |
-----<-------------------------------------------<-----------------------------------------
You CAN however make an oscillator that has a fixed phase shift relative to the incoming signal:
signal 1MHz -->-- phase comparator -->-- loop filter -->-- VCO (= voltage controlled oscillator) ----->-- phase shifter carrier relative to input
| |
^ |
| |
-----<------- programmable delay line ------------<---------------
sets the phase shift
Of course then you may just as well delay the input signal directly:
signal 1MHz ------>--------programmable delay line ------>----- phase shifted carrier relative to input
Sure did. It is used for a whole lot of things, a lot of it is induced
by ATM adaption layers. At your best did you really understand DQLB? I
couldn't quite follow the statistical math at the time.
Yes, that is called Asyncronous Transfer Mode (ATM).
How well do you understand [snip] ?
Understand
that every header pointer refers to one or more octets (bytes) never a
single bit; thus no bit stuffing.
It's called a pointer movement. ATM is just one of many payloads that
can be carried by SONET, although these days the few new SONET
installations typically do not carry ATM. We're still selling new SONET
gear (that I designed almost a decade ago), but only into old
installations, and not very often. Our ATM sales stopped years ago.
In any case, none of this refutes Miso's statement that justification is
used to account for frequency differences.
How well do you understand [snip] ?
Pretty well.
Understand
that every header pointer refers to one or more octets (bytes) never a
single bit; thus no bit stuffing.
Byte stuffing (as in SONET) or bit stuffing (as in many PDH systems), in
either case justification is being used to account for frequency
differences.
I must thank you for the deep belly laugh I got from "I happen to have
read various [...] standards."
Allan
Really? The whole system is plesiocronous.
AMI has problems with long sequences of zeroes, so for DS-1 they use
B8ZS which "stuffs bits" to improve data integrity, not to correct for
clock differences. They also use B3ZS for DS3 for the same reason.
Clock synchronization for such systems uses other methods than simple
bit stuffing.
