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question about trunk lines

Viewing 15 posts - 1 through 15 (of 39 total)
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  • #34251
    simon wang ICQ:83003331

    hi everyone, i am a ip engineer,
    i’m new to voice technology, recently i’m involved in voip projects.

    some concepts realy confused me:
    1. what is a channelized E1/T1 lines?
    2. is there an “unchannelized T1/E1 line”?
    3. what is an “analog call”? do u mean the “local loop” is analog or
    do u mean the “trunk lines” is analog? in my country almost all trunk lines are digital, so there is no “analog call” at all?
    4. if i want to set up a call center, i have to apply for a trunk line from telco, right?
    5. how many kinds of trunk line can I apply from telco?
    a “E1/T1 line” is same with “ISDN PRI line”?
    6. i read on cisco website: “channelized T1/E1 lines” can not receive “ISDN call”, is that true? and why?
    7. i want to ask again: what at all is an “analog call”? which part of it is “analog”?

    thank you very much!!!
    my ICQ :83003331



    Hi Simon,
    To answer all ur questions I’ve to write a separate book of 100 pages!. Anyway……

    Channelized E1/T1 is the one that carries Voice 30/24 channels. And these Channels are muxed…….

    Whereas unchannelized E1/T1 is that u get a raw bandwidth of 2Mbps/1.544Mbps.

    “Analog Call”… what I understand is that it is different from ISDN call which is digital.. and may be as u said it’s due to “local loop” is analaog.

    If u wanna setup a call center u’ve to apply for IPLC line from ur Gateway Service provider and also with other end Gateway service provider. And IPLC is going to be RAW bandwidth and it depends on how ur using it, I mean compression/technology etc….

    E1/T1 is not same with ISDN… but the bandwith is same E1 has 2mbps BW, same as Euro ISDN, and T1 has 1.544Mbps, same BW as American ISDN. The diff. is that in ISDN line one channel in 32/24 is dedicated for siganaling, whereas in E1/T1 it’s not. E1/T1 uses CAS (Channel Associated Signalling).

    haa……I’m tired….

    Hope this helps……



    1 OK
    2 OK
    3 OK plus
    E1 uses TS16 as CAS channel (it uses 4 bits for line signalling). EuroISDN uses a 64K Dchannel. That means it´s the same in BW dedicated to signalling but protocols are a way too different. E1/T1 Register signalling is done by dual tones in each voice channel. See q.421 422& 424.
    E1/T1 are digital systems as they transmits bits, but when you talk about voice, each sample represent tones or sounds. It’s clearer when you need to transmit data or fax over it. If you have E1/T1 every byte should be converted from/to a tone (Modem) If you have ISDN you need a Terminal Adapter and there is no Digital from/to Analog conversion.
    Analog Call is done over a line to/from a home without ISDN (despite of being converted to digital in some parts of the Telco). You can set up analog lines in a PABX.

    If you want to set up a Call Center you can get analog lines programmed as PBX, E1/T1, E1/T1 fractional (the same technology without all channels), PRIs. It depends on your switch and your provider.

    What Cisco says it’s true for data calls (DDR or backup lines) but not for voice calls: You can call from an ISDN phone to a call center with T1/E1.


    Hey guys,

    How do you arrive at the number of IPLC lines required after determining the number of T1 lines?


    hi all,

    i am interested in this topic.

    a few questions :
    1. what is the diff btw pax, pabx and dlts lines?

    2. how to dimension a tel sw if i have the traffic intensity in ccs of the did trunk and outgoing trunks?

    3. any good webpage for the tel sw design. simple pages will help.


    Hope this can help you:

    1. PAX (You mean PBX?) is just a small exchange that needs support from Publich switches to work, normally are name multiline equipment. PABX is a small exchange with more functions that makes a similar work like a public exchange but in the private side. (Hope it helps)
    2.Sw is dimensioned using Routes (trunks), lines (if any), services, all this mean first of all the Topology network you want to design, after that next step is to look for a system that covers network topology and the performance you need (CCS, traffic etc)

    Send me a email if further info is need


    This article was very very informtive.I want to have a question

    1. why is this so that E1 system works in non-us and T1 in US/japan only??

    whats the reason behind this?

    guys once again thanks for such a nice info.

    Prabhakar verma

    US has always tried to set up their own standards in any filed u take .They define thier own standards(ANSI) ,while japan has to follow US so as to make equipments for US and survive .while the whole europe sit together and make their own standards called ETSI and then came we people questioninng the very fact of both the system existence . so we turned up to ITU to form the STandards in TELECOM.

    J. Donson


    Could anyone tell what is “Integrated Digital Access” (IDA)? I have heard about several types of IDA, such as IDA/M, IDA/P, IDA/R and IDA/C. What are their difference? What’s the relationship between IDA and channelized T1/E1?




    is it mean 64*1024 or 64*1000 bits

    Please reply me at

    Sunil Kumar

    Defnly 64*1024.



    Balakrishnan S Naicker

    >>>>1. why is this so that E1 system works in non-us and T1 in US/japan only??
    Is it anything to do with fibre-optic transmission rates SDH (European)& SONET (American)

    I am new to Telecom. Please excuse me I am wrong.

    Balakrishnan S Naicker

    >>>7. i want to ask again: what at all is an \”analog call\”? which part of it is \”analog\”?
    In PSTN (Public Switched Telephone Network), Subscriber lines carry analog signal where as other lines (Trunks) carry Digital.

    Plz point out if i am wrong.


    Can any body tell what are the differents steps when we swith on our mible. if any body can expalin
    the signalling steps i will be very happy . I want to know this information

    Sunil Kumar

    Hello Balakrishnan,

    Are you a Tamilian ?

    When PCM Technology was developped Europe Opted to Make it as a 32 Channel System Whille US Designed 24 Channel Ssytem.

    32 Channel System is called as E1.
    24 Channel System is called as T1.

    Becoz of the good market in US , Japaneese comapnies copied the same idea of 24 Chs PCM to Develop Systems and to use also.

    Just Like any other product Japan Followerd US’s A…

    Later this Tranportaion Technologies were Developped for Optical Medium.SDH Was developped for E1 and US Developped SONET to accomadate T1.

    But I heard that somehow SONET is greater than SDH.( Any Info guys ??)

    Regarding Analog Call:-

    You are correct.But nowadays there are lot solution for Digial Subscriber Lines.Ex:DSL…



Viewing 15 posts - 1 through 15 (of 39 total)
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