Asterisk/FreePBX Analogue and/or Digital Lines?

I have installed my server with the latest Centos Asterisk and FreePBX distro. I am able to navigate to the web based FreePBX configuration screens and have configured some incoming and outgoing SIP trunks. I can make and receive calls without any issues over these SIP trunks.

I now want to connect up our main BT telephone line for incoming and outgoing calls using our established company phone number. We currently have a single BT analogue line.

My question is regarding the best hardware route to take. Should I stick with our analogue line and buy an analogue card with the appropriate FXO and FXS ports or should I get BT to change our analogue line to an ISDN line (if so which type?). Cost is not a major factor I just want the best setup with the best call quality and the most flexibility. I think the ISDN route is the best way however can you recommend BRI/PRI and the correct/best hardware to interface with this?

Many thanks

If you aren’t using the same line for your data (such as Internet) I don’t see what advantage there would be to converting it to an ISDN. If you’re just looking for voice calls then just get a card or gateway and be done with it.

You COULD keep the same number and just transfer it to your VOIP provider and get rid of the analog line completely. Personally I like to keep an analog line as a fail-over in case the Internet goes down and for 911 routing but you will need a way to hand off calls to your VOIP in case the analog is busy. Just a simple roll-over line should do the job.

IMHO there are many advantages to converting to ISDN,

If we speak of BRI (basic rate interface), it is still normally delivered over a single pair (U interface) , the restriction is that you need to be closer to the CO (exchange) than an analog(ue) line limit.

You will normally get two 64k clear channels so two concurrent voice calls and two separate phone numbers.

Either B (bearer) channel can be used for voice or data, plus you can bond 2B+D to 144k for pure data, depending on what TA (terminal adapter) you choose and who your Provider is.

These channels are digitally (the D in ISDN) so all the old problems of tx/rx level and fxo tuning are pretty well gone as there is no “analog hybrid bridge” to worry about, the TA will take care of providing that “hybrid” back to analog if you choose the right TA (the ones with an RJ14, nicely pre/de-mphasized to ALAW or ULAW, on them for connecting your old “princess” phones to :slight_smile: ) (very useful for power outages)

The 16k D (data) channel carries the signaling “out of band” so calls are “built up” and “torn down” almost instantaneously, CLID is also delivered over the D channel, so normally it just works without muss or fus and the caller doesn’t need to wait two rings before your phone rings, or a few minutes to hang up until the co sends out it’s beep beep beep “you forgot to hang up!!” signal.

If money is of little importance then ISDN PRI (Primare Rate Interface) is definetly the way to go, 30 (23 in NANP land) concurrent 64k channels for voice or data, as many “phone numbers” as you care to subscribe to, plus all the previously mentioned advantages.

In either case the TA needs power to work, some vendors supply BRI over a “wet pair” that supplies that power. Germany where ISDN is the norm has the better manufacturers of TA’s due to their experience, I would keep away from cheaper and more oriental adapters/clones as they always need a computer and power and have been known to not always work so well :wink:

Emergency services - 911, is 999 and or 112 in the UK, so I infer that cdsJerryw is from NANP (North American Numbering Plan) land where the local loop is usually a lot longer than in Europe, (The length limitation is similar to that of DSL and it’s varients, but the two data services are mutually exclusive of each other, be aware of that!) and where BRI’s are almost unheard of.

So although the technology came originally from AT&T (Bellcore Labs.) it just never was practically deployed in the U.S. except perhaps for the entertainment industry, I have many clients using one or more BRI’s in their Hollywood Hills home studios, going live on air all the time, there are no delays as happens when the cheaper Internet based solutions are tried.

Basically the quality of service and sound is very much better than any analog line can be.


I had an ISDN line at my house in US in 1995. Since we did not pay for local inbound (I am in the ISP business) I could keep the channels pinned up and bonded. Used a dedicated IP address on the RADIUS record so I could have a routed subnet at my house. 128k of symmetric bandwidth in 1995, it was major geek land.

ISDN was the only switched service that ever actually worked other than dialup. I don’t know anyone who got Switched Multi Megabit Data Service to ever work. Frame Relay and ATM were cell based networks but not truly switched.

With ISDN you could make point to point digital calls.

Most folks don’t even know what a PRI is and think it is just a voice technology.

(Ah, the good old days! When men where men and sheep where nervous!!)

And I a centrex (foreign exchange) BRI in 1994, 144k bonded all day for free to my servers down town (the down side I was 4 digits away from too many others), hmm, the servers where only connected dial-up themselves, but only did phones and satellite connections then 144k for my son to play “Where in the World is Carmen SanDiego”. We lived in the boonies but luckily there was a new (can’t remember the service) fiber extender from PacBell at the end of my road. All his buddies had the latest and greatest 56k winmodems, (suckers!!, lucky if the got 28k) It cost me more grilled cheese sandwiches than I care to think about as they all came round to “see Luke and his high speed machine”, PTP only worked at 56k though outside our CO. I had a numb brained parther for years who refused to believe that a T1 was not necessarily a “pry” but always was a DS1, and he thought he was a Nortel expert, (still does I believe).

Same Provider, PacBell in those days tried to sell me a Switched Sonet ATM connection, the cost was “cheap” at only local milage rates per 64k channel used (45M/ 64k? Holy S^%$), when I asked which way round the ring I was being charged for, they where a little confused.

My first home brewed telephone was to my buddy a “few houses down”. a carbon mike/headset with a battery connected with a one wire connection (unwound from an old transformer winding) with a 6 volt “lantern” battery in series and an “earth” return (I was in England) I think that was in about 1913.

Beat that geekiness Scott!!

(Hmm again, CRS waning, the TA’s where from Gandalf (because the did 144) , and the PacBell imitiave “Pronto”)

Hmm, not sure I can beat that geekness. I had my ham ticket in high school and the amateur club at my school (it was on a college campus) had a really slick voted and simulcast repeater. I talked a two way shop into donating some old Motorola voted receivers and a controller cage when they updated somebodies system to trunked. We uplinked on UHF for the 2M repeater. Hand built the tone encoders and decoders (can you say lissajous patterns).

Unfortunately while I was soldering and playing with my dual trace scopes, my buddies were smoking dope and getting laid so I missed out on a huge cultural experience. I had to wait until college until I could talk some girl into coming back to my room to check out my Corvus 5M hard drive that ran the RCPM archives. Gotta go with what you got.

I can’t complain, got my pilots license and loan sharked to all the drunk losers. Now it’s cool to be a geek, who would have thunk.

Are you coming to Astricon?

Pretty damn geeky there too, I was playing with over the horizon TV-DX, fun in Europe as we had Secam, 819 lines, PAL(I-IV), 625 lines even the good old BBC with 405 line system, at least they were all epilleptically friendly 25/50Hz. signals, well a tad less actually, it’s those old damn leaky electrolytic caps that started all that, The Russkies even had a polar orbiting satellite system for their ultra-boreal citizenskis. I wonder who reset the dish every 30 minutes after a bottle or two of vodka.

I still can narrow down the continent I am on when I wake up in a strange hotel after a hard nigh’t geeking, by listening to the flourescent lights)

I never did find that matching geekess though . . . Oh well. I have to put up with a 50Hz. Lithuanian artist instead (Ow that hurt (singular Hz ?) !!, don’t read over my shoulder!)

Talking of Lissajoux (I’m never sure of the plurality) I am working with a not so young now Luke on an Arduino based x-y servo driven and laser powered cat “pisser-off er”, You should know that cats see green far more acutely than red if you are ever tempted to make one, they seem to be aware of the ultrasonic detector too, that also p’s them off. We are hoping to sell the idea to Roomba.

Look who’s Hi-jacking this thread now :wink:

Yeah well, I think Jerry was like our third trunking customer. He’s a great guy and probably won’t mind. He has a geek streak himself.