[ntp:questions] Convert PPS signal from BNC to RS-232!

Jon Kåre Hellan dev at null.com
Thu Mar 1 14:21:12 UTC 2007

Erling Paulsen <erling at bee.cc.uit.no> writes:

> Hello.
> I have a Symmetricom Syncserver S250 as primary NTP-server. 
> This box has PPS-output via a BNC connector. I need to get this PPS signal 
> onto a rs232 connector.
> Are there any converter kits that can do this, or do I need to make my own 
> "box" for doing this? 
> I have setup a secondary server (ntpd on FreeBSD) that will use PPS to 
> discipline its clock via /dev/pps (on a serial com-port).
> Any hints on how to get the PPS from the BNC(coax)-output on the primary 
> server to the com-port on the secondary server would be appreciated. 

I have seen many designs. One is at
www.kernel.org/pub/linux/daemons/ntp/PPS/TTLtoRS232.ps.gz and uses a
CA3140E op-amt. Another is at
http://www.eecis.udel.edu/~mills/ntp/html/pps.html, but dated
1992. You can also use a MAX232.

Hope this helps.

Jon Kåre

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