> Hi Alex and Joe > > Just to add some more information: > > Be sure that the ISDN circuit is in good balance and that the ISDN IC > have good ground connection and decoupling of supply. The noise can > affect other nearby circuits. Joe's idea with the caps on ISDN have to > be checked according to electrical safety standard because of > restriction on insulation to other circuits. > > The LAN will normally retransmit if a packet is lost. If you use a test > program which indicates every error in communication, I will suggest to > make some real life communication to seen if you have a problem at all. > > Best regards, > > Kim Boll Jensen > Bolls Raadgivning > Denmark > > j...@aol.com skriver: > > > In a message dated 10/8/2002, Alex McNeil writes: > > > > > > > >> As I am in panic mode, is there some guidance out there for me e.g. > >> is it > >> usually a matter of changing the interface IC's or hanging special > >> components onto the lines? > > > > > > > > > > Hi Alex: > > > > This test is indeed a difficult one to pass, but in general the > > transformer-type interfaces that you are dealing with are less > > susceptible than some other types. I have seen ISDN and Ethernet > > interfaces pass this test without the need for extreme measures. In > > the absence of more specific information about your situation, I can > > offer just a few general guidelines: > > > > 1) EN 55024 allows you to use either a CDN or a clamp to induce the > > RF. Some people find that they get more favorable results with the > > clamp than with the CDN. > > > > 2) The interference is applied common mode. In *theory* your > > transformer coupled interfaces will have fairly good common mode > > rejection, but this can be compromised by a bad layout or by some > > types of surge protection devices. > > > > 3) If you have to add some filtering to pass, adding a common mode > > choke is a good first step toward reducing susceptibility. Adding > > caps from each conductor to chassis ground also helps, especially if > > used in conjunction with a common mode choke, with the choke on the > > line side of the caps. Note, however, that high value caps can > > interfere with proper operation of the circuit. > > > > > > > > Joe Randolph > > Telecom Design Consultant > > Randolph Telecom, Inc. > > 781-721-2848 > > http://www.randolph-telecom.com > >
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