[Asterisk-Users] Type of T1 for T100P card

[Steve Underwood]

Hi Josh,

Josh Roberson wrote:

> Cirelle Enterprises wrote:
>
>> ----- Original Message ----- From: "Pedro Aguayo" 
>> <paguayo at teachscape.com>
>> To: <asterisk-users at lists.digium.com>
>> Sent: Wednesday, October 27, 2004 6:18 PM
>> Subject: [Asterisk-Users] Type of T1 for T100P card
>>
>>
>> | I'm currently setting up a PBX system using the T100P card, and was 
>> | wondering if it can handle the 2-way trunk type of T1s. Do 2-way 
>> trunk | T1s use RBS signaling?
>> | Please excuse my ignorance, I have mostly dealt with PRI B and D 
>> channel | type of T1s.
>> | | Thanks
>> | | Pedro
>>
>> I found out by taking the long way around, the t100p requires the t1 pri
>> hybrid isdn bchan, dchan  A standard 24 timeslot t1 will not work.
>>
>> regards
>> greg
>>
>>  
>>
> I apologize if i'm not understanding exactly wtf you're saying here, 
> but if i'm reading this correctly, I COMPLETELY disagree.
>
> I have MANY instances of t100p's on a normal 24 channel t1 (rbs),  and 
> a few on PRI's using standard B and D channels. It will work fine as 
> long as it's configured properly.
>
> -Josh

There seems to be lots of misunderstanding in this chain :-)

The original poster is asking about 2-way telephony. All  the normal 
forms of telephony on T1 can support 2-way operation, and Asterisk 
supports them. However, ISDN and SS7 are more robust than the robbed bit 
signalled forms, like wink start. 2-way just means the same T1 can 
handle a mixture of incoming and outgoing calls on the same T1. With 
high call volumes on robbed bit signalled T1s the likelyhood of incoming 
and outgoing calls clashing (glare) can sometimes be unacceptable. ISDN 
should be rock solid under these conditions.

Your post is also refering to telephony modes for T1s. RBS gives you all 
24 channels, but it doesn't give you 24 *clear* channels. Some bits have 
been robbed. Most commonly ISDN gives only 23 voice channels. However, 
ISDN with NFAS and SS7 can give you 24 clear voice channels with Asterisk.

The middle poster seems to be referring to a data T1. Usually, these 
either have 24 completely clear channels, or no channelisation at all - 
just a single 1.5Mbps stream. He calls this a standard T1. I think most 
people would not, since the more standard forms of T1 are ISDN, SS7 and 
robbed bit. However, it is common for data, often carrying HDLC. This is 
why most recent E1/T1/J1 framer devices have built in HDLC hardware.

Steve