Business Phone Systems

Previous Thread
Next Thread
Print Thread
Rate Thread
#561222 11/12/13 10:38 PM
Joined: Jul 2005
Posts: 1,829
Member
*****
OP Offline
Member
*****
Joined: Jul 2005
Posts: 1,829
normally when i install 70 volt paging mostly Bogen i always use
16x2 shielded cable,
recently i was hired by a competitor to help with a large paging system in a hospital i was surprised that they were not using shielded cable he said that you didn't have to with 70 volt paging.
what is your take on this
thanks

Atcom VoIP Demo
VoIP Demo
Joined: May 2007
Posts: 5,043
Likes: 2
Moderator-1A2, Cabling
*****
Offline
Moderator-1A2, Cabling
*****
Joined: May 2007
Posts: 5,043
Likes: 2
Input cabling is always shielded. Output (speaker) cabling is almost NEVER shielded. The shield can act as an antenna and pick up noise.

Sam


"Where are we going and why are we in this hand basket?"
Joined: Jul 2005
Posts: 1,829
Member
*****
OP Offline
Member
*****
Joined: Jul 2005
Posts: 1,829
makes sense but i wonder why on Bogen web site they say to use shielded thats why i have been using shielded wouldn't unshielded cable make interference on lets say data wires crossing in ceilings ect???

Joined: Feb 2005
Posts: 12,333
Likes: 3
Member
***
Offline
Member
***
Joined: Feb 2005
Posts: 12,333
Likes: 3
I was taught that you never use shielded cable for speakers or 70 volt lines unless the speakers are on an intercom talk back system.

Where does Bogen say to use shielded?

Quote
... wouldn't unshielded cable make interference on lets say data wires crossing in ceilings ect???

Interference with data is an old wife's tale or at least a product of some CGs fertile imagination. I don't care how or where you run CAT5 it's gonna work fine.

-Hal

Last edited by hbiss; 11/13/13 04:06 AM.

CALIFORNIA PROPOSITION 65 WARNING: Some comments made by me are known to the State of California to cause irreversible brain damage and serious mental disorders leading to confinement.
Joined: Jan 2013
Posts: 512
Likes: 1
Member
Offline
Member
Joined: Jan 2013
Posts: 512
Likes: 1
Interference can show up on any 25/70/100v system. I know this because it happened at a School district I use to work at.

Brand new state of the art Fire Alarm system installed along with a Paging system and when they were turned on you could hear the data from the fire alarm system on the paging speakers. The paging system required shielding per the manufacture and the installer ran shielded cable, but didn't connect the shields together. Once the shielding problem was corrected, the data noise went away.

So the end result is do what the manufacture of the equipment requires.

Oh, and never use shielded cable for regular speaker cables as it causes all kinds of problems. You really don't even need to use twisted pair cable. If you are running speaker wire in conduit, just use regular wire the same as you would use for an ac circuit. Otherwise standard 2 conductor cable is just fine at the appropriate gauge.


Patrick T. Caezza
Santa Paula, CA 93060
C-7 - Low Voltage System Contractor - Lic# 992448
Joined: May 2007
Posts: 5,043
Likes: 2
Moderator-1A2, Cabling
*****
Offline
Moderator-1A2, Cabling
*****
Joined: May 2007
Posts: 5,043
Likes: 2
Originally Posted by hbiss
I was taught that you never use shielded cable for speakers or 70 volt lines unless the speakers are on an intercom talk back system.

-Hal

Yup. In that case the speaker (in talkback mode) becomes an input and therefore requires shielded cable.

Sam


"Where are we going and why are we in this hand basket?"
Joined: Feb 2006
Posts: 1,716
Member
***
Offline
Member
***
Joined: Feb 2006
Posts: 1,716
Technically, a shielded cable is actually a capacitor. Think about it and it makes sense. You can cause more problems with shielded cable than you can solve. An amplifier is designed to output into a resistive or inductive load, not a capacitor. Eventually, if the conditions are right, the shielded wire could provide an induced emf back to the finals in the amp and wipe out the transistors.

Some systems, however, are designed with a shielded output in mind. I am reminded of the old nurse call systems and Valcom talkback systems. Both were designed to use shielded cable.

Regarding the new addressable fire alarm panels, I would highly recommend using shielded cable and make sure you separate input pairs from the output power pairs. It makes a VERY big problem if you do not.

Rcaman

Last edited by Rcaman; 11/13/13 01:42 PM.

Americom, Inc.
Where The Art And Science Of Communications Meet
Joined: Jan 2010
Posts: 185
Member
Offline
Member
Joined: Jan 2010
Posts: 185
Hate to beat a dead horse, but I agree, do not use shielding on speaker cables unless the manufacturer requires it for special application such as a school intercom talkback type scenario.

Joined: Jul 2005
Posts: 1,829
Member
*****
OP Offline
Member
*****
Joined: Jul 2005
Posts: 1,829
Hal i cant find it now but i will call Bogen a get an answer tomorrow will update

Joined: Feb 2005
Posts: 12,333
Likes: 3
Member
***
Offline
Member
***
Joined: Feb 2005
Posts: 12,333
Likes: 3
Don't go out of your way, just curious.

-Hal


CALIFORNIA PROPOSITION 65 WARNING: Some comments made by me are known to the State of California to cause irreversible brain damage and serious mental disorders leading to confinement.

Moderated by  metelcom 

Link Copied to Clipboard
Forum Statistics
Forums84
Topics93,736
Posts636,401
Members49,615
Most Online5,661
May 23rd, 2018
Popular Topics(Views)
Today's Birthdays
bfrancisco, FrankV, kreeb, Rik Rodgers, RikRodgers, Rob_Mongan, thoraxe
Newest Members
AMS Technology C, Chrontel, RonZ1971, Michael1948, lllDez
49,615 Registered Users
Top Posters(30 Days)
jsaad 7
Toner 6
Who's Online Now
3 members (intrajm, Nate Ronning, justbill), 39 guests, and 20 robots.
Key: Admin, Global Mod, Mod
Contact Us | Sponsored by Atcom: Business Phone Systems | Terms of Service

Sundance Communications is not affiliated with any of the above manufacturers.
©Copyright Sundance Communications 1998-2022
Powered by UBB.threads™ PHP Forum Software 7.7.5