see inline comments. Anthony Minessale II FreeSWITCH http://www.freeswitch.org/ ClueCon http://www.cluecon.com/ AIM: anthm MSN:anthony_minessale@hotmail.com GTALK/JABBER/PAYPAL:anthony.minessale@gmail.com IRC: irc.freenode.net #freeswitch FreeSWITCH Developer Conference sip:888@conference.freeswitch.org iax:guest@conference.freeswitch.org/888 googletalk:conf+888@conference.freeswitch.org pstn:213-799-1400 ----- Original Message ---- From: Michael Collins <mcollins@fcnetwork.com> To: freeswitch-dev@lists.freeswitch.org Sent: Tuesday, February 5, 2008 6:34:50 PM Subject: Re: [Freeswitch-dev] TDM questions: OZ, signaling on digital spans <!-- _filtered {font-family:Wingdings;panose-1:5 0 0 0 0 0 0 0 0 0;} _filtered {margin:1.0in 1.25in 1.0in 1.25in;} _filtered {font-family:Courier;panose-1:2 7 4 9 2 2 5 2 4 4;} _filtered {font-family:Wingdings;panose-1:5 0 0 0 0 0 0 0 0 0;} _filtered {font-family:Tahoma;panose-1:2 11 6 4 3 5 4 4 2 4;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in;margin-bottom:.0001pt;font-size:12.0pt;font-family:"Times New Roman";} a:link, span.MsoHyperlink {color:blue;text-decoration:underline;} a:visited, span.MsoHyperlinkFollowed {color:purple;text-decoration:underline;} span.emailstyle17 {font-family:Arial;color:windowtext;} span.EmailStyle18 {font-family:Arial;color:navy;} _filtered {margin:1.0in 1.25in 1.0in 1.25in;} div.Section1 {} --> From: freeswitch-dev-bounces@lists.freeswitch.org [mailto:freeswitch-dev-bounces@lists.freeswitch.org] On Behalf Of Anthony Minessale Sent: Tuesday, February 05, 2008 6:19 AM To: freeswitch-dev@lists.freeswitch.org Subject: Re: [Freeswitch-dev] TDM questions: OZ, signaling on digital spans It's a trickle-up methodology. The low level driver interprets the voltage change or the bits flipping or whatever and turns it into driver specific events which in turn are changed into openzap specific events by the zap_<whatver>.c zap_zt.c, zap_pika.c etc. when you apply a signaling to a span in the mod_openzap config the signal specific module will monitor the span for these events and decide what they mean in reference to whatever signaling type it represents. Okay, so the driver-specific events get captured and translated… Makes sense. Curious: does this all happen at OSI layer 2? I don't know exactly how it works. so voltage changes on zaptel card zaptel specific ring event is caught by zap_zt.c openzap ring event is queued on the channel and event data flag is set on the span. zap_analog.c sees the event data flag and gets the ring event on the channel ring event is sent up to mod_openzap who starts a channel in freeswitch. so implementing another sig type like e&m just requires zap_em.c and proper interpretation of the bit shifting events. I belive zaptel drivers and pika can do it but I don't know if the native sangoma can yet. I think I get it. Next question: on a digital span that is set up in the <analog spans> section of openzap.conf.xml – does zap_analog.c do the signal translation even though the span is technically digital? It almost sounds like zap_analog.c is agnostic to the analog/digital nature of the span simply because it’s receiving events from the driver via openzap… Last question: if zap_analog.c is handling the translation of FXO/FXS signaling then couldn’t we almost just copy zap_analog.c to zap_em.c and then redefine the bit patterns that represent on-hook, ringing, hangup, etc.? Or am I oversimplifying again? ;) Yes that is more or less correct. In fact once you took out all the analog state machine etc from zap_analog.c zap_em.c will be rather tiny just starting calls when it gets off hook and ending them when it gets onhook. Thanks for the explanation – I will distill this thread into it’s components and add it to the wiki when we’re done. -MC P.S. – the zaptel drivers do support E&M, E&M wink, etc. I’ve used E&M with the orange splat and connected to my NEC PBX with the exact same tor2 and trunk-side T1 card. Anthony Minessale II FreeSWITCH http://www.freeswitch.org/ ClueCon http://www.cluecon.com/ AIM: anthm MSN:anthony_minessale@hotmail.com GTALK/JABBER/PAYPAL:anthony.minessale@gmail.com IRC: irc.freenode.net #freeswitch FreeSWITCH Developer Conference sip:888@conference.freeswitch.org iax:guest@conference.freeswitch.org/888 googletalk:conf+888@conference.freeswitch.org pstn:213-799-1400 ----- Original Message ---- From: Michael Collins <mcollins@fcnetwork.com> To: freeswitch-dev@lists.freeswitch.org Sent: Tuesday, February 5, 2008 1:39:13 AM Subject: [Freeswitch-dev] TDM questions: OZ, signaling on digital spans Guys, You better run for cover because Mikey has been reading technical books again and now he has questions! J First, I was reading in Matthew Gast’s T1 – A Survival Guide about channelized T1’s and channel associated signaling. Just to make sure I am understanding it correctly – CAS and robbed bit essentially refer to the same thing on a channelized T1 don’t they? The bits that are robbed include the signaling bits – AB or ABCD depending on whether you have SF or ESF. Please confirm if I am understanding this correctly. Second, aren’t FXO and FXS signaling on a digital channel really just a matter of interpreting the meanings of the A and B bits being high or low? Obviously there isn’t an actual loop start or ground start on a digital channel, but rather just a nomenclature for deciding that a particular combination of A and B bits being high and/or low has a meaning, like A high + B low means on-hook in one signaling type but could mean ringing in another signaling type. Again, correct me if I’m wrong… Third, if FXO/FXS signaling is just a matter of manipulating the AB bits in CAS, then shouldn’t it be relatively easy to add E&M signaling since that is essentially just another set of meanings for each AB bit pattern? Or am I oversimplifying it? Last question – how does OZ, in zap_zt.c, determine the signal start type? (E.g. see code starting at line 87.) AFAIK it is not set in openzap.conf.xml nor in openzap.conf. Does it get that info from the zaptel driver? I know the start type is set in zaptel.conf, I just didn’t know if the OZ was smart enough to figure out the start type without requiring the user to specify it in a conf file. Thanks for letting me ask all these questions! I’ll do my best to update the wiki as appropriate as I get the answers… -MC -----Inline Attachment Follows----- _______________________________________________ Freeswitch-dev mailing list Freeswitch-dev@lists.freeswitch.org http://lists.freeswitch.org/mailman/listinfo/freeswitch-dev UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-dev http://www.freeswitch.org Be a better friend, newshound, and know-it-all with Yahoo! Mobile. 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