Caller ID Card issue

[telllman]

Client has a MICS with 60 ext. 12 lines. Line 3 was dead first card. Dialtone present from telco on terminal but dead on sets.Proven to be card. installed new card problem fixed.

1 month later line 3 dead again, went in dialtone at system but not on sets, took card from line 12 (3rd port not being used) swapped with first card problem fixed.

1 week later- lines 1-4 dead. Telco lines have a big hum and static on first line dialtone on 2,3,and 4 at system. Nothing on sets. Powered up and down no difference. replaced card with new card all okay.

card taken to our office to be tested later in the day, all ports work. ???????????? Seems to be a telco issue with surges but what are the cards doing working and then not ??? help

 

[exsmogger]

The newer model CI trunk cards are susceptible to high line current. Most carriers will do nothing about high line current, so you'll have to install current limiters. mikesandman.com carries these.

Normal current is about 25-30 mA. More than 35-40 mA can fry the trunk card. You can measure the line current with a multimeter to see if this is what's causing your problem.

Brian Cox
Oregon Phone

http://www.OregonPhone.com

http://www.linkedin.com/in/briancox1952

 

[telllman]

but the card now works again so what happened to it for it not to work on site

 

[exsmogger]

There is some protection built into the cards, so when current rises too high it will take the line out of service. If the current is excessive it will short out transistors and/or IC's on the trunk card.

Brian Cox
Oregon Phone

http://www.OregonPhone.com

http://www.linkedin.com/in/briancox1952

 

[deadringer22004]

Anything wrong with puttinga a 100ohm resistor in series with both legs of the line? That's what I did and it seemed to work for me.

 

[exsmogger]

That should work. It will serve to reduce line current and keep the line balanced.

Brian Cox
Oregon Phone

http://www.OregonPhone.com

http://www.linkedin.com/in/briancox1952

 

[deadringer22004]

I have had 3 customers that have had this problem and all 3 have been within approximately 500' of the central office. If they are farther away it does not seem to bother the cards.

 

[telllman]

So just so I can explain to client- The boards if they get hit with high current on line side can shut down if necessary. So like a built in protection feature. The card seems fine so I will keep this one and they can have mine I guess ???

 

[exsmogger]

Correct. Too much current can damage the board. The older LS/DS (NT5B40) and CI (NT5B41) could stand up to high current better than the newer cards because they have electromechanical relays instead of IC's.

Brian Cox
Oregon Phone

http://www.OregonPhone.com

http://www.linkedin.com/in/briancox1952

 

[hdingman]

I've just punched in the 100 ohm resistors on the 21X in place of bridge clips. 1/8W or 1/4W work fine. Like deadringer, these were clients within one city block of the CO.