[time-nuts] Nortel GPSTM TP13 positive or negative?

[Taka Kamiya]

There is a typo in my first post.
TP13 as well as one pulse every 2 second output are negative logic.  Manual does not mention polarity of 2sPP.
On this page: Nortel GPSTM - i3Detroit  if I'm reading the circuit diagram correctly (really a construction diagram), he seems to be inverting it once, then feeding it to parallel of another inverters.  If I do this, I get negative 1pps.  I cannot make heads or tails out of scope screen shot as I have no idea (I can only guess) which trace represents what output.  But green line is showing negative logic.




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Nortel GPSTM - i3Detroit


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--------------------------------------- 
(Mr.) Taka Kamiya
I'm stuck in a wormhole....  Hello, worms! 

    On Friday, April 12, 2019, 11:01:02 PM EDT, Taka Kamiya via time-nuts <time-nuts at lists.febo.com> wrote:  
 
 I was fortunate enough to buy Nortel GPSTM at very good prices.  This is a distant cousin of Thunderbird as far as I know.  However, it being CDMA clock source, it's second pulse output is actually once every 2 seconds.  According to various Internet sources, TP13 on board is 1 PPS.
I measured TP13 and it actually IS 1 PPS.  However, this test point is giving negative logic.  Normally +5V and it goes to 0V every 2 seconds.
Manual does not say anything about this being PP2S (with a bar on top).  

Has anyone noticed this or am I doing something wrong????
I cascaded two inverters (74AC04) and have used two gates to provide boost to obtain normally 0V and goes to 5V every 1 second.  It works but I am baffled.  Can anyone tell me what I am seeing is actually the way it is?

--------------------------------------- 
(Mr.) Taka Kamiya
I'm stuck in a wormhole....  Hello, worms!
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