sundance-communications.com/forum Forums TDM Business Telephone Systems NEC Telephones & Systems Telco destroying my DSX (UPDATE)

First problem was that CO was sending 60hz ring signal. Once it was changed to 25hz the DSX would ring. I thought this was the whole problem-- I thought that the DSX ports were blown when I pressed a line button when the CO was ringing and the DSX didnt know it. As soon as I tested it another port blew (DSX was ringing this time).
If the DSX answers the ringing line during a ring cycle, some or all of the ring voltage seems to be passed right thru. (I can hear it on a system phone when answering) On a butt set its not nearly as noticeable. It seems the butt set trips the ring signal much faster than the DSX. The co lines come out of a MUX. Telco was on-site and swapped the mux line card to no avail.
I brought out a DSX80 and it took quite a few calls but I blew a port on it too. I tried changing all the timers and loop lengths with no luck. Loop current is high at 80ma and I reduced that to 25ma with same results. Telco is willing to try anything except bring me copper lines from co! Is the MUX causing this? I'm desperate for some info here. The customers POS Executone system that I'm replacing never had this problem-OF COURSE! Steve

Tell the TELCO guy(s) that they have not given notice of their change of equipment characteristics, as required by the FCC.

Get their supervisor out there with the mux manuals and a trouble phone number for the manufacturer.

As for the Executone, I thought it had lost a couple of c.o. ports. Guess why!

If the mux doesn't ring trip instantly, it HAS a problem!

How did you reduce the loop current?

Any chance the mux is partially programmed as ground start? I've seen that cause ALL KINDS of line seizure problems! John C.

I put some resistors in series with the line to reduce loop current. The MUX serves almost all residential phones except for this business. The MUX tech is very helpful and showed me a printout of the programming although it was pretty greek to me-- he said it was pretty generic.
The big question is why is the butt set tripping the ring much better than the DSX. I can even press a ringing line key on the DSX and quickly press Speaker to hang-up and the line starts ringing again! But no matter how quick I flash a butt set it answers every time. Thanks for the ideas! Any more? Steve

Yes, the mux unit is the problem.

Good luck fighting city hall.

Loop current is out of range period!!!

You should not have to reduce the loop current.

Give MIKE SANDMAN a call @ 630-980-7710 . for advice and suggestions for your issue.

Is the telco a local cable company? I have found with Cox cable, they often times set their ring type as "Trapazoidal". Have them change it to "Sinezoidal".... this should stop the passing of ringing voltage when answering the call.

Mike Sandman is the right call for this one. He sells loop current regulators that will eliminate the problem.

It's a damn shame that us techs still have to fight overloop suurents in this techie day and age, but it's a fact of life. I've had 3 clients in the same small town with the same telco all have this issue. POS telco can't even provide calling party disconnect (pads their time on call since they bill by 6 seconds).

Get some loop current regulators and save your equipment.