[VoIP] DP-compatible ATAs

[Steph Kerman]

Chad Perkins wrote:
> On 28 Dec 2006 at 17:55, Steph Kerman wrote:
>> Bearing in mind that I have 100 real PSTN DID #s and at some point 
>> want to allocate some of them to at least one of the SXS units, I 
>> also want the CNET #ing plan to overlap the PSTN #ing plan. When 
>> calls are extended throught the XB to the SXS I'd prefer to have the 
>> DP outpulsing of real wirespring sender audible to the caller, not 
>> ersatz "recorded" outpulsing sounds from an * box.
> Holy crap. What does one do with 100 DIDs?
20 numbers were 3X the price of 100 numbers so 100 seemed to make more 
sense.  40 are assigned to EXTs on my PBX. The other 60 are on my intercept.
> And what do you terminate them on?
A crossbar PBX.
> I can understand that, however Asterisk nativity will not add nor 
> remove outpulsing "sounds"; whatever goes in one end comes out the 
> other ...:
Asterisk DP outpulsing will not produce authentic sounding DP towards 
the caller as was generally heard for DID completions to SXS 
Centrex-CUs.  While it may not mask it, if the wirespring DP sender has 
to be there anyway to produce authentic sounds, the * becomes 
dispensible for this purpose.  And the W-S senders are infinitely more 
fun to watch!
>> True but I believe that machines that inherently have metallic 2W 
>> trunks should be connected directly together and not go back and 
>> forth between 2W analog and 4W digital any more times than necessary.
> That's your choice. Although I know it can be done, no one I know is 
> doing 4W on Asterisk.
I think you missed the point.  * is inherently 4W.  Therefore any 2W 
analog line or trunk termination involves a 2W/4W and 4W/2W conversion.
> Myself I prefer to think E&M trunks are a better way to go (instead of 
> FXOs ... and Asterisk does support E&M via channel banks).
>> As long as my DID trunk is delivered on analog copper, I won't be 
>> inserting an * between the PSTN and my switches for this reason.
> I can understand that and that makes sense for a small set up.
The monthly cost for bringing in a T1 to have the DID delivered 
digitally is completely unjustifiable.
>> I have no objection to inserting an * between an inherently 4W 
>> digital medium like CNET and my switches.
> The VoIP part of CNET is a TCP/IP medium and I would suggest is 
> neither 2W or 4W per se; however CNET is 2W for most folks at the ends.
These things are inherently 4W in the basic meaning of the words: 
separate paths for each direction of transmission.  I'm not talking 
purely about the interfaces between specific pieces of equipment.  The 
term "4W" is commonly understood to mean both.  Microwave is "4W" even 
though it has no wires.
> :
>> In the context of the switching environment under discussion, that's 
>> true as long as you don't object to going back and forth 2W analog 
>> and 4W digital N times.
> N=2 (one depending on how you do the math) just like in the PSTN. 
> What's the difference between going through an Asterisk or going 
> through a 5ESS? If you call someone next door or in the next state it 
> goes 2W-->Digital-->2W same with CNET (unless the end point is a 
> digital set/IP phone). It is duly noted and you are on the record in 
> that strict 2W local usage is the way to go for you and possibly others.
I stated that since I want the analog DID trunk to be able to reach both 
XB and SXS lines and since it is best not to insert an * in this 
inherently 2W analog path, I see no benefit to inserting an * tandem 
between by XB and SXS switches since that would introduce additional 
2W/4W and A/D conversions that provide no benefit.
> However, as a couple have pointed out, there are some advantages to 
> having Asterisk in the middle. And for those who choose that path I 
> don't think the digital transition is any great sin.
>
> Now if you front ended 1B/1R lines with Asterisk like it was a PBX 
> then I supposed you could make the argument that there is a second 
> digital transition... well that's life. Commercial PBXs do the same 
> thing in this situation. Myself I think if I had a 100 DIDs I'd be 
> bringing the bulk of them in on T-carrier and keep things digital as 
> far as possible and eliminate the extra digital transition (so in this 
> scenario Asterisk would actually reduce the number of digital 
> transitions).
Ah!  Apparently you are confusing DID #s and DID trunks.  I have 100 DID 
# terminating on a trunk group consisting of 1 trunk.  If I had 100 DID 
trunks it certainly would be cheaper to have 4 or 5 T1 spans.  I could 
not possibly afford that.  It would be pointless for these hobby purposes.

Steph