Hi, everyone: I am developing a system using Asterisk, TDM-400 analog cards, analog lines, and Polycom SIP phones for internal extensions.
Initially there was bad echo but after a series of efforts, I've managed to reduce it to a negligible level (it only happens when both parties speak simultaneously, and even there, only for a few hundred milliseconds). From an echo standpoint, things are very satisfactory. The HPEC has been very effective. The remaining problem is extremely variable volume, particularly as perceived by our internal callers. The remote party is often, but not always, too quiet. I've determined that it depends heavily on where that remote party is. - If the remote party is on a circuit on the same local exchange, the volume is perfect or nearly perfect. - If the party is on a remote exchange, the volume can vary, from barely audible, to audible but still too quiet to be really comfortable. In these cases, the users will crank the handset or headset volume on their Polycoms to make the remote party audible, but that ends up causing distortion which is bad enough to be irritating. The volume level does seem to depend on the exchange. For instance, all calls to a specific exchange are at the same general volume level. Now, standard analog sets have a varistor circuit to compensate for these variations in signal level, but it would appear that the TDM cards don't incorporate this kind of dynamic gain control. Zaptel allows you to control the transmit and receive gain at the interface card, but isn't that what fxotune is supposed to do? Tune those gains so that the echo is minimized? I don't want to play with gain only to undo the echo tuning done by fxotune. Does tinkering with the gain undo the tunings done by fxotune? Similarly with ztmonitor: Is tinkering with the gain using ztmonitor going to undo the tuning done by fxotune, or can I do both? Have you encountered gain issues like this on analog lines, and if so, how did you address them? Is cranking the rx gain on the Polycom phones a viable solution, or is it likely to make echo worse? I've tried a few adjustments, and they seemed to aggravate echo; once even so badly that the remote party could hear echo. -Stephen- _______________________________________________ --Bandwidth and Colocation provided by Easynews.com -- asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
