NEC SL1100 - Calls vanish then come back

[dbm0011]

Hello Everyone,
Thank You for your replies in advance.
I have a client with an SL1100 / analog lines out of an Arris Modem from Comcast.
Arris modem has been replaced 2 times,,
Calls on all lines,, randomely,, intermittently,,, will loose for lack of a better term... "signaling" and call will go to just "Air" in the back ground and then come back.
I was on the line with the office manage today and she said it happened 2 times during our call. I did not notice the call going away as i was talking to her from my cell phone driving down the road.
could this be a loss package or line supervision thing like on a Nortel system ?
does this sound like it is leaning toward the Arris modem having an issue ?, or does it sound like the SL1100 having an issue ?
any help is greatly appreciated.
Thanks
Don

 

[Ragnorak]

If you didn't do the trunk calibration, try that.

http://www.necsl1100distributors.com/techtips/SL/78/Trunk-Calibration-and-Conditioning

Check the settings in 15-02-12 for off-hook signaling and make sure there isn't anything set to beep in the handset. Also make sure that the carrier doesn't have call waiting set on the lines.