Log In

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


DID trunk vs CO vs TIE also start methods?

DID trunk vs CO vs TIE also start methods?

DID trunk vs CO vs TIE also start methods?

So when I call and order an analog line they don't ask me if I want a DID or CO or Tie trunk. They don't ask me if I want loop start immed start, wink start or a jump start :).  

That leads me to believe that I can configure a line any way I want. IE, I can make a loop start CO trunk a wink start DID trunk if I want to.

Is this correct or am I missing something here?

RE: DID trunk vs CO vs TIE also start methods?

phone primer time.

you have two main divisions of copper lines for a phone system, DID or Trunk.
DID = Direct inward dial this is where your phone system sits there and listens to the did trunk for digits from the telco that will tell the phone system how to handle the call and where to send the call.  with DID your system will provide the line voltage to the telco and this is normally immediate start. this is one way only.

trunk.  this is basically the same thing as a phone line at your house. when you have a call the telco sends you a ring and you answer by taking the phone off the hook (loop closure) you can start a call by taking a phone off the hook (loop closure) and the telco will send you dial tone to let you know that they see you.

on trunks you can also use ground start where one side of the copper pair is momentarily grounded to initiate the start of a call or acknowledge the ring from the telco.

you also mentioned TIE lines, these are special trunks that normally are configured between two phone systems using 4 pairs of wire to pass the voice and control, one pair is used to send voice from system 1 and to receive voice on system 2, the second pair is used to receive voice on system 1 and send voice on system 2. the third & fourth pair is used to control E&M signlalling M signal indicates a call going out and e signal indicates a call coming in

I am sure i missed some nuances in this quickie but this is to give you the basic idea of the trunk types. (BTW I think that jump start is what I gave my daughter last month with a dead car battery)

as for what you need that will depend on two things. first your phone system, some systems are not designed to handel ground start, some have to have different cards depending on what type of system you are going to use, as a design tech I normally depend on what the phone system or if replacing a system on what was pre-existing at the site.

second is that different trunk/line styles cost different and it depends on what the customer is willing to put up with for paying the phone co.  DID is much more expensive to set up and pay monthly than POTS service )plain old telephone service)

time for you to find some reading material thne curl up with it for  a while, try an online search for "how telephones work" as a starting point.


'Rule 29', "The enemy of my enemy is my enemy's enemy. No more. No less."
Communication Systems Int'l


RE: DID trunk vs CO vs TIE also start methods?

Thanks Jerry,

I knew much of the technical stuff but couldn't understand the process behind it. In other words do I have to order a line as a DID or can I configure any POTS line as a DID? You hit that question near the end. So I guess the phone company just expects you to know what you want when you call and order a line, because they never ask.

Hope you noticed the smiley after the jump start reference...:)

RE: DID trunk vs CO vs TIE also start methods?

You need to know what to order before you call telco. The most precious time you can spend to guarrantee victory on an install or upgrade is with the end-user discussing all these possibilities jerry clued you on. THEN being available, or in the background when the order is placed.

Adversity is Opportunity

RE: DID trunk vs CO vs TIE also start methods?

A POTS line is a two-way line (both DID and DOD) thus no need for the provider to ask you. No need to ask you if it's wink start, loop start, ground start - or starts at all - because it does't go to a PBX where you program that. It's all done by the phone company, just like a telephone line to your house.You'll just plug in a phone at your end.

If you want to have those questions asked to you - order a CO trunk. They should ask how many lines you want in the trunk group as well as all those other questions you wish they would. You should have a PBX/ACD to translate too in this case.

Order a DID trunk group (known as ADL LOCI) only if you don't want to make outgoing calls on this trunk.You'll have to buy a range of DID numbers as well.

Order a DOD trunk group (Direct outward Dialing) (known as ADL LOCO) only if you don't want to recieve calls on this trunk. You'll only be able to make outgoing calls.

Order a PRI if you want 23 voice channels (known as bearer channels) and 1 control channel (knows as the "d-channel")
This "d-channel" will carry your signal and framing. This would be an ISDN T1. Then you'll get asked other questions, "Will that be B8ZS and ESF?" - "Which channel do want the control on?" - Two or more T1s, "Which circuit will be index 0, 1, 2, etc.?" "Have you ordered the DIDs?" "How many digits do want deleted?" "Do you want any digits inserted?" "What do you want for a DNIS?" .. and then you should ask, "What are the circuit IDs?" also ask "How many digits do you want to see on an outgoing call?"

You can order a T1 (24 channels) that isn't PRI - it could use 'e&m' signal (known as robbed bit). (Skip a few of the questions in this case.)

The translations for each kind of T1 will be a little different (signal group or not signal group, trunk group form etc) and to be honest I only know how to translate each in the Avaya system.

You can order other services other than ADL LOCI/LOCO on your T1 - (meg8, wats, etc: - ask the provider)

You can order an BRI too, if you don't need so may lines.  

RE: DID trunk vs CO vs TIE also start methods?

Sometimes you call the line providers and wonder if they actually know what they are talking about when they ask all these questions and the answer is NO. The people that do that data entry have such a high throughput that they probably don't have enough time to learn the difference between a DID and a 1FL line. You really need to to specify for them, doing half their job, what you want.

Joe W.

FHandw., ACA, ACS

If you can't be good, be good at it!

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Tek-Tips Forums free from inappropriate posts.
The Tek-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Tek-Tips forums is a member-only feature.

Click Here to join Tek-Tips and talk with other members!

Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close