On 1/26/2006, Peter Tarver wrote:
I am in the process of a product review that I require clarification on whether or not bulk ring generator outputs that supply other equipment are typically earthed, unearthed or a mixed bag. Hi Peter: In North America, the typical way that ringing voltage is applied is called "battery-backed" ringing. For the two phone wires tip and ring, the tip lead is grounded and the ring lead gets the AC ring signal superimposed on -48 VDC. I believe that the way this is typically implemented in the CO is to build a bulk ring generator that has a floating AC output. One side of the output is tied to the -48 VDC battery, and the other side becomes the bulk ring that is bussed to the line cards. So, this bulk ring signal is indirectly tied to ground via the -48 VDC battery. For a period of time the industry experimented with so-called "floating battery" architectures where the -48 VDC battery was floating with respect to earth ground, but only after the call was set up. For ringing to work properly on all types of analog interfaces, it must be referenced to earth ground. Other methods of ring injection are often used outside North America. For example, a common method is to apply just the AC ring signal (referenced to earth ground) on the ring lead, and apply the -48 VDC (also referenced to earth ground) on the tip lead. I'm not sure I answered your question because I don't know what point in the system you are looking at the ring generator output. However, it eventually gets referenced to earth ground before is it applied to the phone line. Joe Randolph Telecom Design Consultant Randolph Telecom, Inc. 781-721-2848 (USA) [email protected] http://www.randolph-telecom.com <http://www.randolph-telecom.com/> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
