On Fri, Apr 30, 2004 at 10:28:02AM -0500, Barton Hodges wrote: > [EMAIL PROTECTED] wrote: > > The real problem arises when : > > - you have some echo induced somewhere (your call goes through a 2 > > wire line) > > - you have some delay induced somewhere (you use VoIP for instance) > > Following the "2-wire to 4-wire causes echo" thought, the following > should not result in noticable echo, true? > > - Analog phone <-> TDM10B-FXS <-> Asterisk <-> TDM01B-FXO <-> PSTN
Yes, because although echo will exist, delay should be short enough so that you don't notice. Never tried such a setup myself, though. Please furthermore note that Asterisk uses "pseudo" TDM. In real telco world, PCM highways that interconnect trunks and devices switch one byte every 8000th/sec. OTOH, Zaptel devices switch eight bytes every 1000th/sec. This is due the to PC bus architecture (it would cause way too much overhead otherwise). So the delay is actually 8 times longuer (at least) than in the PSTN. > - VOIP Phone <-> Asterisk <-> VOIP Phone > - VOIP Phone <-> Asterisk <-> T100P <-> PRI > Nobody's supposed to generate echo on VoIP phones. However, the "PRI" side will probably connect to a 2-wire PSTN set at the remote end, so you will get echo from there. > However, the following could result in noticable echo (as I am > experiencing): > > - Analog phone <-> ATA <-> Asterisk <-> TDM01B-FXO <-> PSTN > - VOIP Phone <-> Asterisk <-> PSTN > Definetly. Although Asterisk (zaptel, actually) make a fairly good job at cancelling it. > What about the following as described in Raymond McKay's setup (Thank > you Raymond) > Does the channel bank provide the needed, and adequate echo > cancellation? > I don't have any experience with channels banks. Not very common stuff in Europe. > > Since you state that echo cancellation needs to be performed closest > to the source, could the Grandstream HandyTone-286 be doing an > inadequate job of echo cancellation? If this is the case, does anyone > have experience with another ATA (Sipura SPA-1000, Cisco ATA-186, > etc.) that does such a great job of echo cancellation, that the > "2-wire to 4-wire" situation is not an issue? Does Grandstream have > improved echo cancellation scheduled for a future firmware upgrade? > The Sipuras are definetly better than the HandyTones. I've heard that the forthcoming GS firmwares will enhance echo cancellation performance, though. -- Nicolas Bougues Axialys Interactive _______________________________________________ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
