sundance-communications.com/forum Forums Other TDM Phone Systems Sprint - Tadiran Telephones & Systems protege HUM

Have a very stable Protege LTX in place for 7 years. About 60 digital stations + ProtegeVoice.

We have confirmed a hum on three different digital extensions that are on three different DDEI cards. Hum occurs on INTERNAL (station to station) calls only. Once you open a CO line to make an outside call, the hum stops on all of the affected stations.

We cabled this building over two years ago. Termination blocks look clean (no sparky work by the client). No new electronics or power supplies near the KSU. Yes, we have tested all stations with good working phones, handsets & cords.

Before we start ripping out station cards, chassis and power supply. Does anyone have any other suggestions?

Swap a DDEI out with another one and see if the problem is still there. If so I would cold start the system and see if the problem remains at default. In my experience a card replacement will fix it. You could move those extensions to different ports to be sure the HUM doesn't follow.

Thanks, 6string.
Update -> We did swap out at least one DDEI card and the hum continued. Before a cold start and removing other cards, we made yet another inspection of the environment and users. Found the main operator was using a headset that was generating a hum that was bleeding into some stations. Further, another source of line noise at just one station was a radiant heater sitting close to the desk set and station cord.

Even though it's too late this time, one step that helps in quite a few issues is using BLOCK CONTROL under Mainenance.

It's amazing how many heaters disappear from beneath cubicles when the Fire Marshall is doing an inspection.

I have had some Protege systems that NEVER have problems and the only time you hear from the customer is... "The person at that front counter si no longer with us...how do you change the Time & Date?"

I have also noticed that computer monitor interference can occur always try moving the phone to the other side of the desk