[time-nuts] Symmetricom TimeSource 2700

Charles P. Steinmetz charles_steinmetz at lavabit.com
Thu Nov 24 23:17:16 EST 2011

Kevin wrote:

>I use the Craft connector for monitoring with BTMon rather than the 
>RS-232 port.
>It appears the Craft output, while spontaneously emitting 
>alarm/events, does respond
>to queries from BTMon on the Craft input.

Everything I reported previously involved the Craft port feeding a PC 
COM port using the RJ45-to-DB9 cable supplied by Symmetricom.

>Do you happen to have a RS-422/485 interface? I don't, but I'm 
>interested to see
>if any spontaneous output occurs on the TOD port.

I have a 422/485 card here somewhere, but I haven't used it (maybe 
even seen it) in more than 10 years.

I poked a scope at the TOD jack.  The TS2500 manual says that (in a 
TS2500) Pin 1 should be PPS (positive), Pin 6 should be PPS 
(negative), Pin 5 should be TXA output (positive), Pin 9 should be 
TXA output (negative), and Pins 7 and 3 should be a 20 V external 
supply positive and return, respectively.

I found PPS positive and negative on Pins 1 and 6.  Logic low is 
about 1.2 V positive with respect to case ground, and logic high is 
about 3.8 V above case ground, for a logic range of approximately 2.6 
V.  The PPS pulses are 500 uS wide with rise and fall times of ~20-25 nS.

I did not see any data on the TXA outputs -- the positive TXA output 
just sits at logic low and the negative TXA output sits at logic high.

There is 20 V between Pins 7 and 3.  As for the unspecified pins -- 
Pin 2 sits at nominally 0 Vdc, and Pins 4 and 8 sit at nominally 
0.168 Vdc.  All three have around 20 mVp-p of hum and noise.

While I was at it, I poked at the RS232 connector, as well.  Pin 3 
(TX Data) has a 16 or 17 mS burst of data every 5 seconds 
(approximately), from -10 V to +10 V with respect to case 
(henceforth, 232 low and high, respectively).  Between bursts, it 
sits at 232 low.  Pins 4 and 7 (DTR and RTS, respectively) sit at 232 
high.  All other pins sit at ground.

Best regards,


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