4-lines, not channels or extensions

I’m working on a phone system for a small office (3 employees) where their current system is basically four separate analog phone lines, each being plugged into 4-line POTS telephones. So when an incoming call rings on line 1, the three employees look around and decide who’s going to answer the phone. When a second call comes in, the second call is “bounced” up to line 2, and the next employee answers it. So far, so good; its a call group.

The trouble is that the active call is present on all three phones, without having to transfer. Any one of the three employees can pick up their phone and chime in on the conversation.

I’ve setup the system with four extensions, and each extension is present on each phone (using 4-line SIP phones), but no dice. I can’t seem to figure out how to get phone B to be able to insert itself into a call without having the call transferred to a separate extension.

The users want to be able to press “line 1” or “line 2” or “line 3” or “line 4” and be able to jump into an existing conversation.

Is this possible?

… by russell on Fri, 03/30/2007 - 22:51

…Emulating Shared Lines in Asterisk

The term “shared lines” in Asterisk means implementing the functionality of having a line appearance on a phone that maps to a trunk. So, multiple phones can have a “line1” appearance that is mapped to a SIP trunk, for example. Then, when any phone is using this line, the line shows as in use on all of the other phones.

So, after enough demand for this feature, we decided that we would commit to making a way to set up an Asteirsk system to work like a key system. There was a version of this support in Asterisk 1.4.0. However, it didn’t really work. So, before 1.4.1 was released, I completely re-wrote the SLA support for Asterisk. Now, it works!

link http://www.asterisk.org/node/48342

The Polycom 550’s have four line keys. You can monitor another extension status with them and the icon will change on the LCD.

I would program 1 of them for a ‘pickup’ and program a soft key at the bottom for ‘park’ so you any station can park a call and have it picked up by another station.

As far as barging in on a conversation, you can’t do that. In fact most modern key systems don’t allow you to pickup a busy line. You need to train the users on how to conference in the broker to a call.

This sounds good… I’ll give this a shot this evening.

Here’s the scenario:
All calls to the office are ultimately calls for the broker. The phone rings about once every 10-15 minutes, and the broker takes those calls directly when the phone rings. If the broker is on the phone or away from his desk, someone else in the office answers the phone and takes a message. Often times the broker will be on the phone when another call comes in and asks the other party to hold on a second to see who’s on the other line. More often than not, the secretary will answer the phone if the broker is on the other line, abut then the broker clicks over to see who the new caller is.

There really isn’t a way (without a: yelling across the office, or b: a convoluted series of button pushing) for the broker to check in and see who the new caller is and decide which caller he wants to call back in a few minutes.

I realize that there is a certain logic for how FreePBX operates, but we also have to be receptive to the nuances of how each business operates and cater to their needs, without dictating a new set of parameters within which they “should” operate.

All they would have to to get the second agent in on the call is dial 2nd agent’s ext. When he answers, hit conf. and your all on. Then Agent 1 can drop off at any time. Busting in on a call is absurd.


When the secretary answers the call she can ask who it is and then call the broker on his open line. He can put his call on hold and talk to the secretary and she says so and so is on the line. If he wants the call she transfers it. You can spins as its way more professional.

I hear you… and these are all good “work around” solutions which I will present to the broker. However, they are all a compromise. What you see as “Professional” the broker sees as an impersonable customer experience.

His clients are his livelihood, and the way he runs his business is his prerogative. He runs that office, and wants to be in control of his domain, not be at the mercy of his secretary to conference him in to a call… that’s too involved… too many steps.

Surely you can understand his perspective and what he’s trying to accomplish…?

Similarly… what if your teenage daughter was up in her bedroom talking to her boyfriend on the phone, and you wanted to pickup and say hi. Sure you could call her “extension” and ask her to conference you in, or, as her parent, just pickup the phone and say hi… maybe less “Professional” but maybe also more “Personable”

Nobody ever said that an Open Source PBX is a perfect fit for every business. During the evaluation period you as the integrator should have determined that the system did not match their work flow.

We are in that stage right now. We are still considering which option to use. We are looking at a few other options too. I’m just surprised that Asterisk has left such a large void in it’s capability.

I have been a proponent of shared extension appearances for a long time. The Digium/Asterisk crowd is not interested in providing this functionality; nor, apparently, is the bulk of the user community. I’ve said many times that if SLA was available, Asterisk could begin to knock Nortel, Avaya and Siemens out of the picture.

Please do not confuse FreePBX as being part of the Asterisk core engine. FreePBX is a GUI that writes configuration files for you. If the functionality does not exist in Asterisk, it is certainly not the fault of FreePBX that you cannot accomplish a goal.

Many would like to see a “Square Key System” ability and many others would like to see the more complex Shared Call Appearance or Shared Extension Appearance in Asterisk. Until enough people bang away at the Digium folks and either offer money or contribute code, this will not happen.

I’d try to find a used Avaya Partner system to do what you’re trying to do now because, in the meantime, what you want ain’t happening with Asterisk.

as a matter of fact, that’s what we’re trying to replace… go figure.

Well, it doesn’t. It’s an Asterisk and not a FreePBX issue.

Certainly if you Google “Asterisk, Shared Extension” you will find more complaints and information than you care to read.

SIP does not directly support this feature however Broadsoft published extensions that are supported by many manufacturers. Asterisk moved support for this feature into the possible 1.8x candidates however support seems to be moving away from the request and I doubt it will make it in.

The issue is “key systems” as you describe don’t scale well. The very low end market of small key users is not a very large niche and installing and maintaining a server for under 10 extensions does not make much sense. It certainly is not a money maker. My experience is IT guys try to do this on the side with little or no experience and end up pissing off the customer.

The real application for shared lines is the manager/admin relationship where a manager or admin can place a call on hold or have an appearance of the managers line.

Lastly, I don’t know what type of phones you are running but have you looked at assigning parking keys to your BLF keys? If trained right most users are happy with this compromise as they can see a light lit to pick up the parked call.

Okay, so objectively…

This is a real estate office. Often times the Broker (the boss) is on the phone when another call comes in. When the secretary (or another agent) answers the phone, the Broker often places his call on hold (or quickly wraps up the current call) to see who the new call is.

In the absence of SLA, is there any way to indicate on phone B that phone A is in use? (ie, if the Broker’s office door is closed, how does another agent know whether to take a message or forward the call to the Broker?) (Voicemail is too impersonal for this office; they like to take messages.)

How would a switchboard operator be able to see which extensions are in use, and which extensions aren’t?

Ehstein - What type of phones are you using? As I mentioned BLF’s and parks do exactly what you want. Asterisk fully supports BLF’s (busy lamps) and directed call pickup.

zeusvh - You would be in rare company if you got the chan_sla module to work. I don’t know anybody who has. Certainly it is not supported by FreePBX. I have been meaning to try again in Asterisk 1.8, however I have not seen any commits to that code in awhile and would be surprised if the situation has changed drastically.

We’re using Polycom 550’s. What we need to be able to achieve is for the business owner to inject himself into a conversation that his assistant is having. Our attention is less focused on how to route incoming calls, rather how to handle picking up a call on “line 1” without having that call transferred to any particular user.

That’s very disappointing. I’m surprised that nobody’s caused a fuss over this functionality yet. Is this something that’s within the capabilities of the SIP protocol? Would there possibly be an add-on module that would provide this functionality.

I guess the trouble that I’m having is these office folks don’t “need” a new phone system. They like the way they operate now. If I want to sell them on a few new features (IVR, follow-me, vmail, etc), I still have to be able to provide “legacy operation”. I can’t believe that Asterisk wouldn’t have this functionality.

Asterisk does not support Shared Line Appearances, what this feature is called.

You can’t do what you are trying to achieve.

Kenn, What about the SLA as detailed here: https://wiki.asterisk.org/wiki/display/AST/SLA+Configuration

Have you tried it?

SLA is not shared call appearance. It is shared trunks. While it might marginally work in some instances (on Asterisk 1.4) it is not what the general user community is looking for. The Asterisk SLA implementation is not readily scalable, not supported by FreePBX and is poorly designed compared to the operation of most non-Asterisk systems.

The Broadsoft standard for shared call appearances is much more what the user community wants but has been shunned and ignored by Asterisk developers. There is an apparent wall of opposition within Digium (and amongst many Asterisk resellers) when it comes to shared call appearances.

The Broadsoft standard needs to be added to Asterisk and then the FreePBX folks could also tackle the GUI side of making it work.

It just seams like it should be easy… we already know how to conference call, and we have ring groups.

When an incoming call hits FreePBX, it enters a conference call room. If there is only one outside caller in a conference call room, than a particular ring group is triggered.

That way, whenever anyone picks up that “line” they are entered into that conference call…

I’m sure it’s more complex than that, but if I can make it work on the client side with a series of button pushes (conference calling between telephones), surely we can write a few lines of code that will do it for me automatically…?