Jan, cat 5 and cat 6 are performance categories for connecting hardware in generic cabling acc. to ISO/IEC 11801. The RJ45 jack is only part of the connecting hardware. Usually you will find circuitry for compensating crosstalk on the printed board. This is necessary to achieve the desired performance category for all 4 conductor pairs in the connector. If you need no more than 2 conductor pairs use pins 1 and 2 for one pair and pins 7 and 8 for the other pair. 40 dB at 100 MHz is for crosstalk between the inner pairs on pins 3/6 and 4/5. This is the worst case for crosstalk. Using the proposed configuration you can achieve 80 dB at 100 MHz with a slope of 20 db per decade, without any compensation. Kind Regards Thomas ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu