Wilton Helm wrote: one thing I missed mentioning about fxs devices - the linksys/sipura ones actually allow you to set line characteristics on the slic inside it. you can vary from the 600ohm default, and tweak gains a bit. Some mix of a capacitive line or different resistance may help. never tried myself but there are a ton of things you can play with.
> There are a lot of factors that impact this. First, CAT 5, while > usable is overkill. Cat 3 (otherwise known as I/O wire) works equally > well for voice grade lines. That being said, for that long a run, a > heavier gauge wire would be better. I believe telcos use 18 – 22 guage > (Cat 5 and Cat 3 are both 26 awg). This has less resistive loss. > > Most FXS or ATA devices use 24 volts or less for “battery”. That works > fine for short loops, but limits the range. A central office POTS port > normally uses 48 VDC which works well to several KM. If the customer > is at the end of a long run in a rural area, they use a “long line” > card which uses 75 volts. (In rural communities, they often place the > line cards in a roadside “remote terminal” and use statistically > multiplexed T1s to make it appear to the switch as a part of it. > > That addresses the DC characteristics, which can be reduced to ohms > law. A phone needs around 8 V @ .02 A. The wire resistance determine > the drop (E = IR) and the source voltage determines whether there will > be enough left. The A.C. characteristics are more complicated. The FXS > must do a 2 wire to 4 wire conversion, which involves matching the > impedance of the line. The FXS is generally designed for relatively > short lines, so might not be able to match either the resistance or > capacitance found in a long run. Heavier wire will minimize this. In > addition to that, the transmit side of the 2 wire to 4 wire circuit > must be able to drive the load it sees, and again it may not be > designed with a long run in mind. Finally, COs line cards have the > ability to adjust receive and transmit gain to compensate for sound > level losses in long lines. While this isn’t routinely done on simple > circuits, it is an option an FXS doesn’t generally have. In addition, > the more gain that is inserted, the harder it is to balance to 2 wire > to 4 wire circuit, and the more complex it has to be in order to > support this. > > Wilton > > ------------------------------------------------------------------------ > > _______________________________________________ > -- Bandwidth and Colocation Provided by http://www.api-digital.com -- > > asterisk-users mailing list > To UNSUBSCRIBE or update options visit: > http://lists.digium.com/mailman/listinfo/asterisk-users _______________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users