our phone company doesn’t provide polarity reversal. i tried using callprogress option but it’s unreliable since we’re outside the USA. i found out that they’re sending 16khz tone as Answer Supervision signal AND as a timing pulse for their coinphones.
i know 16kHz (or 12khz) is beyond the detection of zap channel at 8khz sampling rate. is it possible to implement detection in zap/zaptel by temporarity sampling at 32khz then revert back to 8khz after answer? is there any FXO device or channel bank that implements this feature on hardware?
i highly doubt you’ll get much of anywhere with 32khz. Also, if your question is not answered, try bumping the existing thread instead of posting another.
I think your best bet would be to either get a polarity reverse answer signal from the telcom or hire an EE guy to make one. For an EE (electronic engineer) it shouldn’t be too hard to create a device that will listen for the first 32khz tone and then wink the line.
the other way people have done it is using silence detection…
i didn’t mean to detect the 32khz tone but rather sample the line at 32khz to detect the 16khz/12khz tone (nyquist rate). whether this is possible or not in zaptel, at least i know if i hv to look for other solutions just like ur suggestion. i hv seen a chip that detects these tones. it’s okay for 1-2 lines. but if u hv a dozen of them, whew, it’s gonna be tough for my level. i just hope it’s possible in zaptel because pulse metering is widely used in europe.
i am not a dev but i imagine that would involve a significant change to zaptel itself, wouldn’t count on too much support unless you are willing to put up a bounty…
does your telco refuse to give you polarity reverse connect/disconnect supervision?
in that case, a hardware solution is eminent. our telco provides polarity reversal disconnect signal but no polarity reversal during answer.
i might hv a PLL detection ckt that switches the A-B line upon detection of the first 12khz/16khz tone. then i can enable answeronpolarityreversal on zapata.conf.
[quote=“LanVox”]in that case, a hardware solution is eminent. our telco provides polarity reversal disconnect signal but no polarity reversal during answer.
i might hv a PLL detection ckt that switches the A-B line upon detection of the first 12khz/16khz tone. then i can enable answeronpolarityreversal on zapata.conf.
tks for the input.[/quote]
Hi LanVox, I was following your problem with great interest because I have the same identical problem and couldn’t find a solution so far. I kind of got the feeling that I might have to go for a hardware solution too… but didn’t find anything so far.
This device you speak of… is it available in the market as a product or is it something you plan to build?
there are available pulse meters esp in europe but it needs addntl ckt to reverse the tip and ring wires. so, it’s a diy project.
i already hv the detection ckt. i can add the polarity reversal switching ckt using relays. but we still hv to know how FXO reacts to the debounce during switchover. anyone who can comment on this? otherwise, we hv to use a mercury-wetted relays or use a more expensive solid-state relay.
i hope pulse metering will be included in FXO cards because it’ s critical in billing applications e.g. hotels, etc. Alcatel’s Omni-PCX has 12khz/16khz metering capability. it’s really cool.
[quote=“LanVox”]there are available pulse meters esp in europe but it needs addntl ckt to reverse the tip and ring wires. so, it’s a diy project.
i already hv the detection ckt. i can add the polarity reversal switching ckt using relays. but we still hv to know how FXO reacts to the debounce during switchover. anyone who can comment on this? otherwise, we hv to use a mercury-wetted relays or use a more expensive solid-state relay.[/quote]
I have tried my card with lines that DO have reversal activated. In that case answer detection works perfectly. However I need to find a way to work without Telco reversal because the service is not offered universally.
I totally agree with you that FXO cards should support pulse metering. I find it hard to believe that such a critical feature has been ignored and not demanded by many other users. Even with non-billing scenarios, answer before pickup can cause many difficulties in normal PBX operation.
I hope we can keep this topic alive till the community finds a workaround or affordable hardware that supports the function.
When I called verizon to see if my line had or could have answer supervision with polarity reversal, I couldn’t find anyone who knew what I was talking about.
I’d certainly love to know of any custom solutions out there. In the meanwhile I use backgrounddetect. I have found for my system, waitforsilence can error out if the sip connection is not perfect.
mike, we can keep this going by bumping the poll i created on the other thread. but it’s only for 1month. i agree that we keep this going to get attn of the FXO suppliers. perhaps our int’l users can help snowball this feature.
i think it has to be a hardware solution cuz it’s an out-of-band signal. sampling the line at 32khz via software would be too much. there are chips made by CML that implements this CMX631A and CMX641A.
dghunt, perhaps u were asking non-switching people at verizon. testing for pol reversal answer supervision can be easily done in zapata.conf using answeronpolarityreversal=yes. if the line has no polarity reversal, asterisk will disconnect even if the called party answers.
i still hv to locate the URL where i found the DIY pulse metering detection ckt. i’ll post it next time.
it needs an addtnl circuit that will reverse the TIP-RING wires feeding to the FXO (the phone set) upon receipt of the first pulse only. the logic should reset the reversal ckt upon loop disconnect. but the BIG question is: will FXO tolerate any switch “bounce”? can anyone comment on this? because this will affect the design of the switching ckt. tks.
for exchanges feeding 12khz metering pulses, it can be done by changing the values of some resistors and capacitors.
this issue have been sidelined for quite some time. i’ve bumped this post because of the things i recently discovered with the capabilities of the zaptel cards.
i found out that that the Silicon Labs DAA chips used in TDM400P and X100P HAS PULSE METERING FEATURE. pls see the datasheet
it’s referred to as Billing Tone Detection feature.
so the cards are hardware ready UNLESS there’s a blocking filter on the card! so, it’s just a matter of upgrading the driver to have this powerful feature.
anyone who has a need for this feature like hotels, outgoing call centers, our European friends, please speak up.
Thanks a lot for the info you provided, I have the same problem, and I am looking for a solution for it.
In your last message, you mentioned “it’s just a matter of upgrading the driver to have this powerful feature.”. Would you please elaborate more on this?
I have a digium TDM400P with 4 FXOs on it, I can tell that the FXOs are Si3050 chips. I am pretty new to voip and this kind of chip stuff, and I would really appreciate it if you can shed more lights on how to update the driver.