# CLOCK RECOVERY from an ASYNCHRONOUS signal? low-level student question

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#### hfss_newbie

##### Junior Member level 2
Hi guys,
after several years of studying telecomm., i still have problem understanding basic things.Every while & then i have to return to my univ. books to re-learn the basics. that's what I did yesterday with no succes!
Here is my question about recovering CLOCK from an Asynchronous signal sent by TX. You guys are my RX. Please try to find the bit rate from my PURE DATA signal.
Tell me what signal shapee you want me to send since i'm your TX.
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-Assumption 1: TX(myself) uses RZ (return to zero) coding. There is no JITTER and no parasite.it's a very basic simple case.
( if the above picture is not shown correctly, i have attached an image):
I'm sure that having this signal is not enough to recover the clock(bit rate).
So if you need me to send you another signal(call it FLAG or etc) don't hesitate to ask me.I will be glad to send you the following signal PERIODICALLY.
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- Assumption 2: RX knows the signal shape of PERIODIC flag

1-Should i tell you guys (RX) with which freq. I send this PERIODIC FLAG SIGNAL?and if so, Should I say it in
number of bits(e.x every 8 bits) or in freq.(each 3 seconds)?

2- How you(RX) can recognize if it's the FLAG and not the PURE DATA itself?

-Assumption3 : Regarding Q2.I can send you a FLAG signal that has better characteristics( Minimal autocorrelation except in zero,little cross-corelation with data)

I have read that we can find the clock rate by looking at TRANSITIONS on data signal.but How?

3-Assumming that you figure out the bit rate, now you're able to read my WHOLE binary signal(e.x.110000111011...). DO you now seperate the FLAG signal (you have its shape & clock=> you have its code) and extract the PURE DATA?

Thanks very much for all contributions

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