[VoIP] [C/O X-Bar] Seattle Museum Switches

[Steph Kerman]

Duncan Smith wrote:
> [ Crossposted to the VoIP list and the CO/XBAR list; please don't 
> crosspost replies unless you have a good reason. :) ]
>
> On Sun, Jun 03, 2007 at 09:33:37PM -0400, Steph Kerman wrote:
>> Do you have listings of the source code and/or configuration data?
>> Are you modifying the load image or what are you doing to get it working?
> Right now we have a listing of most of the CBLM (Common Base Level 
> Monitor), which is the main call-processing loop that dispatches 
> program control. It's essentially cooperative multitasking, where each 
> task is required by contract to take 5ms or less per go-around.
Is this what needs to be modified for the smaller configuration of the 
museum system?
>> It would also be good if you recorded the acoustic call completion 
>> sounds adjacent to the equipment. When I visited the equipment I was 
>> surprised at how much the acoustic sounds overwhelmed what I heard in 
>> the handset. Especially true of the motor and shaft noise around the 
>> Panel office. It completely changed my perception relative to what I 
>> was accustomed to hearing in the handset from the days when I had 
>> service from or access to lines on working Panel, #1XB and #5XB 
>> offices. IMO, it's instructive to be able to hear the sounds in the 
>> handset only, with no acoustic noise present, hear the acoustic only, 
>> and hear them both together with an appropriate balance between the 
>> two so that neither one masks the other.
> My favorite idea for making recordings is to put the handset audio on 
> the left channel, and the office audio on the right channel. Then the 
> synchronization is nearly perfect, and the listener can decide how to 
> mix it.
That's a good idea!
> On my to-do list is writing a program to record such audio. I have 
> this apparently disgusting piece of hardware in my laptop, called a
> "winmodem". It functions under Linux as a sound card with a "mute" 
> control that actually is a hookswitch control. It's basically an FXO, 
> for which I have much more use than a modem.
Why write anything?  Why not use the sound input jacks, coupling to the 
line with an external device.  There are genuine WECo off-the-shelf 
items that would do this task well.  The museum probably has one sitting 
around.  Manual dialing for making the calls to be recorded is probably 
more convenient than dialing through the PC just as turning a volume 
control on a speaker is easier than changing the volume in Windows.  
Replace the transmitter on the phone being used for the test calls with 
a resistor to avoid picking up acoustic noise through the handset 
transmitter.
>> At such time as you have an * working at the museum, it might be 
>> interesting if you hosted remote ATAs which got dial tone directly 
>> off the museum switches without any active role by the *. "Nailed up" 
>> connections in other words. This would allow people to make calls as 
>> though connected directly to the switches regardless of where they 
>> were to hear what call completion sounds like. Nothing would be 
>> masked by the * for calls initiated this way.
> I think it would be reasonably easy to do this. I think the best way 
> to connect it is to use a T1 concentrator, and (so far as I know) it
> is possible to connect different channels of a single concentrator to 
> different switches.
>
> What's a good single-T1 line interface card to use with Asterisk? 
> Digium's Wildcard TE120P looks good, but I'd say that it's a tad
> expensive. (I don't know what the budget is, but I don't think it 
> includes $600. Sad face.)
These days it sounds like a Cisco 3810 hosting a channel bank full of 
FXO cards is probably the best and most economical choice but it's not 
something I've been following closely.  For one FXO port from each of 
the switches: Panel, #1XB, #5XB, SXS, North CX and #3ESS, perhaps the 
Cisco alone would suffice.  Not sure what the available configs are for 
the 3810.  ISTR hearing mention of 6 analog ports.

SK