Crosstalk and radio stations

[Sarlen]

Greetings everyone,

I have a strange issue today, I have 3 users reporting they can hear a radio broadcast on their headsets when they are not on a call. I went down to take a listen and sure enough it sounds like a oldies station playing really really low. The sets are 3905's with the standard Hello Direct headset/amp. Has anyone come across this before?

 

[thattekguy]

Is there any radios in the area,make sure all the doors are on the PBX, sometimes you can pick up EMI interferance if they are open.MOH maybe playing close by the switch..something like that.

 

[johnpoole]

that is usually rfi.. emi usually is just a hum.. might make a diff if your googling for a cure.. couple of things i usually do with either... your using 3 or 4 pair cat 5? ground all the spare pair.. if you have an idf between the switch and the sets, that is the best place.. if not in the switch room take a ground from the power ground, the cable sheath ground (inbound telco) and earth ground.. if possible bond that back to a cold water pipe... that's 4 sources for a ground, try to get to at least 3 of them.. then take a jumper looped to the vacant conductors of the used station wires...

what your trying to do is all a sheild that will capture the inbound signal prior to your headsets using it as a source to the amps.. bad cabling, cat 3, splices etc will all add to the problem.. silver satin to long (50 feet plus) make a perfect quarter wave ant... the sound is not on one wire, it's .0002 milli amps on each of them.. the headsets are bumping it up just like a cheap radio.. this was a common problem when we started replacing key systems with electronic key... we had filters (small caps) for analog stations.. for digital adding grounds to sheild the source was the best cure..

i had a cust that told me not to make it go away just get the c&w music off the phones.. just change the station..

john poole
bellsouth business
columbia,sc

 

[Sarlen]

They think they found the issue, the switch was not grounded properly. They ran a new ground but we wont know for sure until its nice and damp/overcast.