data center - monitoring dry contacts for security system

[Denver Osborn]

Not sure where I could've posted this as it seems too off topic for an hpux thread, anywho...

Is there anyone out here who's worked with remote monitoring products for dry contacts (to monitor things like fire alarms, security, ups)?

I need something that will monitor a dry contact's NO/NC state and send out an email or snmp for any alarms that would be set off.

So far I've only found products from one vendor http://www.akcpinc.com but am hoping to find others for comparison.

If you've used any similar products I'd like to hear feedback on ease of use and configuration.

Thanks!
-denver

[A. Clay Stephenson · Accepted solution]

Hi Denver:

You are making this way too hard. All you have have to do is connect the dry contacts
to a serial port. I typically let the contacts detect DSR so that an open() will block until DSR is asserted. Typically I let the contacts close the circuit between RTS (that is an output already asserted) to the DSR input. The open() system call then succeeds and you know the contacts have closed. These two lines are the only ones you need in the cable although I almost always tie the shield to CG (Chassis Gnd) on one end of the cable to reduce noise.

Off the top of my head complete with timeouts and usage this was about 50 lines of C. I'll try to dig it up if you are interested.

I use the same technique to monitor HVAC contacts, generator contacts, and fire/intrusion alarms which in turn feed VP/O.

[Denver Osborn]

Hi Clay,

Thanks for the info! Right now I believe we monitor a generator's dry contacts using the serial port on one of our systems. I'm not completely sure why it was decided to get another device for monitoring.

If you have that program you mentioned, I'd really like to have a look at it as we can compare it to our existing setup.

Thanks again!
-denver

[A. Clay Stephenson]

Well, it's a little bigger than I remembered but it's still quite modest and does include a usage section.

compile it like this:

cc checkport.c -o checkport

Use it like this:

TIMEOUT=5
PORT=/dev/ttyd2a6

checkport -t ${TIMEOUT} ${PORT}
STAT=${?}
if [[ ${STAT} -eq 0 ]]
then
echo "I was able to open port ${PORT}; that's good or bad depending upon whether you use normally closed or normally open contacts"
else
echo "I was not able to open port ${PORT} within ${TIMEOUT} seconds; that is either good or bad news"
fi

Invoke as checkport -u for full usage. It is important that you use a devive node that is configured with full modem control (i.e a dian-in modem). I did check ny notes and the contacts actually complete the DTR (Data Terminal Ready) Output to CD (Carrier Detect) input connection. The open blocks until CD is detected. Disregard my earlier
DSR to RTS connection.

Depending upon the modem hardware used, the block on open can be something of a load so it's usually best to poll every minute or so and let the open timeout rather than blocking forever on an open but that's up to you.

[bill lab]

denver -

try my company, General DataComm (GDC).

we make a terminal server product called "ADT" that has 8 dry contact inputs and 2 outputs. It can send SNMP traps and can perform remote site management at the same time, and alot more.

Here's the link to the datasheet from our site.

http://www.gdc.com/inotes/pdf/scadt_ds03-072_eo.pdf

(fyi - i'm in engineering not sales - our products are designed and manufactured in the U.S. of A.)

hope this helps!

- bill in CT