Hi all,
When configuring Asterisk with an ISDN card, it will at one point
become necessary to select the LBO (Line Build-Out) value. This is an
integer (0-7) that is determined by the length of the cable and is
selected from the following table. Many of us are familiar with it:
CSU (dB) DSX-1 (feet)
-------------------------------
0 0 0?133
1 133?266
2 266?399
3 399?533
4 533?655
5 -7.5
6 -15
7 -22.5
The value selected should almost always be zero. However, if the cable
is of a significant length, another value must be selected, but which
one? There are two columns: CSU and DSX-1. When is it appropriate to
use the one or the other to determine the correct LBO value?
Thanks,
Jaap
On Saturday 15 May 2010 19:28:37 Jaap Winius wrote:> When configuring Asterisk with an ISDN card, it will at one point > become necessary to select the LBO (Line Build-Out) value. This is an > integer (0-7) that is determined by the length of the cable and is > selected from the following table. Many of us are familiar with it: > > CSU (dB) DSX-1 (feet) > ------------------------------- > 0 0 0?133 > 1 133?266 > 2 266?399 > 3 399?533 > 4 533?655 > 5 -7.5 > 6 -15 > 7 -22.5 > > The value selected should almost always be zero. However, if the cable > is of a significant length, another value must be selected, but which > one? There are two columns: CSU and DSX-1. When is it appropriate to > use the one or the other to determine the correct LBO value?Each LBO value is a different amount of loss to be expected on the line, and therefore the signal is amplified a commensurate amount. What it really comes down to is what works for you. -- Tilghman Lesher Digium, Inc. | Senior Software Developer twitter: Corydon76 | IRC: Corydon76-dig (Freenode) Check us out at: www.digium.com & www.asterisk.org
Quoting Tilghman Lesher <tlesher at digium.com>:>> The value selected should almost always be zero. However, if the cable >> is of a significant length, another value must be selected, but which >> one? There are two columns: CSU and DSX-1. When is it appropriate to >> use the one or the other to determine the correct LBO value? > > Each LBO value is a different amount of loss to be expected on the > line, and therefore the signal is amplified a commensurate amount. > What it really comes down to is what works for you.That's the usual approach, but if I was still happy with it I would not have asked the question. According to the manual, the values are found in a table, but what good is that if you can't make any sense of it? In the mean time, I've googled some more and found one text that suggests CSU and DSX-1 are both T1 trunk interface types, while another suggests that a DSX-1 is an interface that a CSU is attached to. It seems to me that the table refers to two situations that used to (or maybe still do) occur in North America in which an ISDN card is be attached to a T1 trunk line via a CSU/DSU (the "DSX-1"), or only a CSU. In the latter case, the ISDN card must also act as a DSU. Can anyone say is this is correct? Any further explanation would be welcome. Cheers, Jaap
Quoting Tilghman Lesher <tlesher at digium.com>:> http://www.digchip.com/datasheets/parts/datasheet/222/82V2088-pdf.php > > See pages 17-18 of the associated PDF. While this is not the T1 framer chip > used, the values are identical, which leads me to believe that these values > are actually industry standard.Well, maybe more like a defacto standard. But, it still doesn't explain when to use the different values in a software configuration, e.g. with Asterisk. As a term, DSX-1 is confusing. One description can be found in the Wikipedia article for T-carrier, which says it stands for Digital Signal Crossconnect: "DS1 signals are interconnected typically at Central Office locations at a common metallic cross-connect point known as a DSX-1. ..." On the other hand, articles like the following use DSX-1 to describe customer site connections: * Adtran NetVanta T1 Access Router http://www.arcelect.com/netvanta_access_t1_router.htm The diagram shows how two different NetVanta models can be used to connect a T-1 line to a PBX. There's also this page: * Primary Rate Interface ISDN Line Port http://www22.verizon.com/wholesale/solutions/solution/pri+rate+isdn.html Near the end, under Detailed Information, it says: "PRI service consists of a 4-wire DSX-1 port associated with a local switching system and the 4-wire DSX-1 cross-connect between the OTC DSX-1 termination and the local switching system DSX-1 termination. "PRI ports are DSX-1 interfaces that meet the electrical specifications in ANSI T1.102. PRI service and use B8ZS line code and the Extended Superframe Format (ESF) described in ANSI T1.403." Again, the term DSX-1 is used to describe a CPE port. In such cases, I think it will probably be appropriate to use the "DSX-1" column in the LBO table. Still, what's the difference between "CSU" and "DSX-1"?? Speculation: Could it be that "CSU" refers to situations where there is no equipment of any kind between the demarcation point and the ISDN card? In such cases, the ISDN card will have an integrated CSU, and the length of the cable will be unknown (thousands of feet), but you can know the attenuation value in dB; either by measuring it, or by getting it from the telco. This scenario may only occur in the United States. On the other hand, "DSX-1" will refer to situations where the ISDN card is connected -- via a DSX-1 port and a cable of a known length -- to an external CSU and/or DSU. In turn, this equipment is connected to the demarc. This scenario may apply in all other situations, e.g. ISDN BRI cards that connect to an NT-1. Does this sound reasonable? Thanks, Jaap
Asterisk
2010-May-18 14:23 UTC
[asterisk-users] Play MusicOnHold and continue with dialplan
Hi guys, Is it possible to start playing MusicOnHold to the caller but also continue with the dialplan in single extension, something like this: exten => s,1,StartPlayingMoh() exten => s,n,Wait(10) exten => s,n,Dial(someone...) exten => s,n,Wait(10) exten => s,n,Dial(someone else...) ... Regards, Alex