I have a site which uses a 3rd party dispatch board to answer and transfer calls. The SV9100 hands off the calls via SLT ports.

The problem is 40% of the time the system will skip over the 2nd ring. When listening with a butt set. You hear the first long ring followed by the caller id being sent. Then when the 2nd ring should go through you can hear it try to kind of ring but never sends any voltage and almost sounds like it's being shorted. The other 60% of the time it works fine.

The issue is, if they don't answer the call quick enough. The dispatch board thinks the call has hung up, then when it sees the next ring it thinks it's a new call and receives no caller id.

I've removed all the wiring from the equation. It still does it with only the butt set connected. They have all IP phones so there are not any other cards in the system.
I've replaced the chassis, verified it was grounded, replaced the SLT card and changed the ring cadence to different ones. No change. NEC says there is nothing they can do. If i disable sending of the caller id on the SLT port the second ring always works.

Needless to say I'm it a loss.

Never heard of this. Have you tried to duplicate this in a lab or bench system? Have you removed the hydra cable and gone directly on the port? Also, how precisely is this setup. How are you ringing that SLT port? Is this coming in the system to that port how.....? Have you tried ringing that port directly from a digital phone?

I have duplicated the issue on our in house CP20.
Yes, all cables have been removed from the SLT cards except for my butt set.
It happens if I call the extension directly from a desk phone or transfer from voice mail. Across both cards and daughterboards.
The analog extensions are in a dept group and calls are transferred to the master number but the problem happens when calling the pilot or extensions directly.

I've never ran across this before either but then again most devices I connect via analog ports are fax machines anymore and they usually pickup on the first ring and I don't typically pass caller id through to them.

New software dropped yesterday. You might want to upgrade. I've never seen that.

I did a little more testing this morning.
I had it fail on a completely defaulted system with only 15-03-09 enabled. Tried different software levels from 7 to 12. All had a missed 2nd ring. Sometimes it took 20 attempts but it still was there.

I'll try the new software as well but I'm not holding my breath.

How fast are you placing calls through this? Also have you changed the COS to NOT allow a secondary all on that line? Sounds to me like you may be hooking that line. You need to shut all that off. The other thing is that the cap may be not getting charged fast enough.

Well NEC was able to replicate the issue and is sending it off to development.

When I was doing additional testing, I took a SV8100 SLT card and replaced the SV9100 one I had. Low and behold the problem went away.
I then placed the SV9100 back into service....problem returned. Even tried a UX5000 SLT board which is identical to the SV8100, it worked as well.

NEC verified my findings. So now I either wait for a fix from NEC or upload a migration license for the problem to just go away.
This definitely feels like a hardware issue rather than software.

Thought I'd update my findings as of now.

Thanks for the update. Very interesting.