> > Pull the clone card out of the system and look for the chipset numbers > > on the card. Go to the chip manufacturers web site and find the specs > > for that chip set. The specs will likely tell you the chipset was designed > > for the US 600 ohm impedance telephone network, and if your country's > > telco specs are different (which I'm very sure they are), through away > > the clone card. Without proper impedance matching there isn't anything > > your going to be do to fix the problem. > > I can check the chip on monday, but local telco impedance requirements are > 600 > ohms - just like US. > > > > > > > I'm thinking about playing around with increasing/decreasing resistance > > > by placing additional resistors in the circut. Messy, but if it could > > > help... What do you think? > > > > Adding resistance has nothing at all to with impedance matching. Resistance > > will impact the DC loop, but not the AC impendance. The AC impedance is a > > function of how the chipset was designed. > > > AFAIR, the impedance is not a simple factor, but a combination of passive > resistance plus reactance - which usually varies within measured frequency > range. Therefore channging the device resistance WILL change its impedance. I > know the result will not be perfect, but at least i hope for better load > match than it is now. I assume the specified impedance is required within > PSTN frequencies which will be roughly 100-4khz, right?
That's not exactly true if you think about it. Since pstn lines are typically copper based and have a varying resistance based on the length and guage of copper, the copper resistance will vary from almost zero (close to CO) to values over 1000 ohms. That certainly does _not_ change the AC impedance of the line (regardless of its length); its still 600 ohms. I don't recall for sure, but I'm fairly certain the impedance is relative to 1,000 hz tone. _______________________________________________ --Bandwidth and Colocation sponsored by Easynews.com -- Asterisk-Users mailing list Asterisk-Users@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users