[cisco-voip] FXS voltages / POTS compatibility

[Justin Steinberg]

Are you using local h323 or sip 'pots' dialpeers to route directly between
your FXS and T1 port?  Or is call manager in between the call due to MGCP
or VOIP dialpeers involved in the dialplan ?

I doubt your issue is line voltage, since you can see the call being
placed.  My guess is the DSP is processing the call and causing issues.
I've seem alarm boxes use nonstandard DTMF transmission that isn't properly
recognized by the DSP.

The 2800 supports DSP bypass by default when you route directly between
ports using POTS dialpeers.   You do need to have properly configured
network clock configuration.

Can you send a copy of your config along with the output of 'show
controller t1' and 'show network-clock'

Justin
On Feb 28, 2015 10:33 PM, "chris" <tknchris at gmail.com> wrote:

> Hey Ryan,
>
> We have a channelized T1 with channels split between voice/data so the
> voice path is TDM. We have a VIC-4FXS/DID and for each of the two ports we
> have a single copper pair with rj11 on both ends, one side going to the FXS
> port and the other is going into alarm panel. The total distance from the
> 2800 to the alarm panel is around 20-30 feet and its a direct run, no 66
> blocks or anything in between.
> Don't know model of the panel (this is another location)
>
> From what I've read I think the problem is the default idle-voltage the
> VIC-4FXS/DID is only -24V but based on the link I sent in the first email I
> thought this could be reconfigured through the idle-voltage option but this
> doesnt seem to be available when I try to enter it under the voice-port.
> When I talked to the alarm company and told them I see the calls going
> through the guy told me the alarm doesn't check the line state based on the
> dialtone and he said that it uses the voltage to see when the line is idle,
> ringing, etc and I think this is where the problem lies.
>
> Someone recommend this adapter offlist which looks interesting but the
> price is a little nuts as it costs more than all the equipment we have
> installed at this site combined.
>
> http://www.homedepot.com/p/Viking-1-Line-Long-Loop-Adapter-VK-LLA-1/204399995
>
> Chris
>
>
> On Sat, Feb 28, 2015 at 8:18 PM, Ryan Huff <ryanhuff at outlook.com> wrote:
>
>> Chris,
>>
>> Can you diagram the connections for me?
>>
>> Are the copper pairs swinging off a 66 block before terminating to the
>> alarm panel or is there a direct copper path between the fxs port and the
>> alarm? Are you using an RJ-11 or RJ-14 configuration?
>>
>> Could you estimate the copper distance between the termination points?
>>
>> Is the pstn path for the VG SIP or TOM?
>>
>> Also, I would be curious to know if the alarm panel is a Simplex Grinnell?
>>
>> Thanks,
>>
>> Ryan
>>
>>
>> -------- Original Message --------
>> From: chris <tknchris at gmail.com>
>> Sent: Saturday, February 28, 2015 07:52 PM
>> To: cisco-voip at puck.nether.net
>> Subject: [cisco-voip] FXS voltages / POTS compatibility
>>
>> Hello
>>
>> We have a location with a 2800 acting as a voice gateway where we have 2
>> FXS voice ports going to an alarm system. We are using the vic-4fxs/did
>> line card.
>>
>> We have the alarm company saying they are seeing the panel reporting Comm
>> trouble so we checked the call records and we also did some debugging in
>> realtime and we see the calls are going out and when we plug a test set in
>> the dial tone is good.
>>
>> In talking with the alarm company and researching we have come to believe
>> the issue may be due to the idle and ringing voltages. We came across this
>> link:
>>
>>
>> http://www.cisco.com/c/en/us/support/docs/voice/analog-signaling-e-m-did-fxs-fxo/28280-ring-idle-voltages-fxs.html
>>
>> This looked promising however when we are in voice port configuration
>> node we do not have the idle-voltage setting available. We tried several
>> iOS versions in 12.4 as well as 15.x hut no luck
>>
>> Is this line card not capable of -48 idle voltage? What cards are? Do we
>> need anything special as far iOS version?
>>
>> Ideally we want to have 2 voice ports that are as close to a standard
>> pots line as possible.
>>
>> We are a bit lost as its the first time we have hit an issue like this
>> and we are just hoping someone has been down this path before. If we have
>> to change line cards or even to another platform we are open to it as long
>> if someone has a setup that is known working in this manner
>>
>> Thanks in advance
>> Chris
>>
>
>
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