[Asterisk-Users] ISDN master clock issue ?

[Rich Adamson]

Tristan wrote:
> I 'll make some tests with a TE210P and see what happens, I'll post as 
> soon as I have results...
> 
> Asterisk is planned to be at the end of every PRI connection, providing 
> voip to the PBX and IVR to the customers calling on the 2 E1 lines 
> connected to Asterisk ...
> 
> The MATRA PBX is connected to its own E1 line and Asterisk is directly 
> connected to a secondary S2 bus.
> 
> Setting this S2 bus to be a slave cannot be done easily as we have to 
> manipulate tables inside the Matra PBX...
> I don't know how to do that...

Then hire someone that does.

> Anyway I'll test it and see what happens,
> but if I understand well to be totally sure there'll be no troubles I 
> should buy a Sangoma card no ?

If you design this correctly, either card will work.

If you want to do a complete (and most accurate) test, then simply try 
to send a fax through whatever design you want. If it passes, voice will 
not be a problem.

> Rich Adamson a écrit :
>> Tristan wrote:
>>> The fact is that I have 2 different E1 (euroisdn) providers and an E1 
>>> (euroisdn) connection to a Matra PBX...
>>>
>>> The PBX needs to be master and as far as I know the PSTN providers 
>>> needs it too...
>>>
>>> So I want to be sure that the quad E1 card I'll buy will work without 
>>> troubles in this kind of setup...
>>>
>>> Can I only put the synchro to the PBX and forget about the PRI 
>>> providers ?
>>
>> No.
>>
>> It is highly unlikely the PBX truly needs to be master. If that were 
>> an actual requirement, the vendor would never be able to sell their 
>> PBX into "any" environment where they connected to a E1 provider. The 
>> telco providers "never" slave their equipment from a customer-owned 
>> PBX. You will need to find the option in the Matra PBX to define it as 
>> syncing from the E1. (In fact, I'd bet a small amount of money the 
>> default implementation in the PBX is to sync from any attached E1.)
>>
>> There is a 99.99% probability the two E1 providers obtain their clock 
>> sync from a higher level (hierarchical source), and are already in 
>> sync with each other. If you use a digium card, you select one of the 
>> providers as your "first choice" sync source, and the second provider 
>> as your second choice sync source when the first choice provider's E1 
>> is down.
>>
>> You definitely want your digium/sangoma card to support the 
>> hierarchical design of the digital network, and that well known design 
>> requires you to sync from your upstream provider, and pass that sync 
>> along to your downstream PBX. If you don't do that, calls originating 
>> from the PBX and passing through the digium/sangoma card to the PRI 
>> network will incur clock slips (out of sync). If the clock slips are 
>> too great, you will experience clicks, etc, during a call. Also, if 
>> all the components are not in sync, any use of modems (eg, faxes or pc 
>> modems) will be significantly degraded if not impossible to use.