1A2 KSU emulation...Beyond busy lamp field

We operate Asterisk and Free PBX (V2.10.xxx) using Polycom IP550 instruments. So far we’ve been able to figure out most things. But…

I have several lines which need to ring and appear on differing pools of instruments (extensions) across our system for each line. Each line would ring different groups of extensions/instruments. However, we need functionality like a 1A2 system where any instrument will see the incoming call/flash, ring (unique ringer), ability for any device in the pool can answer, place on hold (not park), retrieve from hold (not park), and terminate the call in addition to transferring to other extensions within the network.

Now, we’re already doing multiple appearances of the same DID line/extension and showing a busy lamp field of that line/extension. But once a call is claimed by an extension, the call can’t be recalled from another extension without it being parked instead simply being placed of on hold. Therein lies the problem.

We have a high turnover of staff who are not the slightest bit knowledgeable of the parking concept let alone train them to park and unpark a call. They get the hold aspect. And in a hurried situation, that level of confusion will be dangerous for our staff and our product.

The need is to simply answer the phone, push the hold bottom to hold the call, show it’s on hold to all the relevant devices, and then be able to press the associated flashing (busy lamp) line on any other phone instrument to retrieve the call. No special codes or other sequence of keys. Ala…1A2 KSU.

As for my skill set, I am a novice at best. We do have a more advanced person available. But they’re on medical leave and we need to move this mission along to replace an aging PBX at one of our other studio/office facilities.


Mike McCarthy

FreePBX/Asterisk are not key system and does not provide the feature you are looking for.

It actually can be done, but it’s advanced:



The 550’s are somewhat Button-Poor so it’s hard to make Parking work on them - with a Yealink or another phone with lots of buttons, it’s easy - we usually create a Transfer Button called Park-It! which is a blind-transfer to 70 and then we will put two or three Park Buttons with Park-71 and Park-72 - Asterisk can show BLF on those and if you look down, nobody is parked, and then you press Park-It! you know you are always going to Park-71.

I think since you are a novice, that the cheapest by far would be a paid copy of iSymphony - $100 for a 20-User copy and then you have visual parking with Caller ID.

Just looking for the path of least resistance.


This is unfortunate that what is a basic telco function in PBX’s isn’t available on what is purportedly a very advanced system between Astrisk/FreeBPX. Has the system forgotten some of it’s most basic functionality? I don’t mean that in a negative sense or to simply wax nostalgia. This is a significant impediment to expanding our business. Parking/unparking calls through various key sequences is more complex than the situation requires…and staff will tolerate.



Really it is not “unfortunate”, FreePBX was ALWAYS designed to be a PBX (Public Branch eXchange) to expand the abilities of the old 6, 10 and 20 button 1A2 sets, much like a very advanced old Centrex system under 1A2 , just don’t expect it to behave like a 1A2 keyswitch, it just won’t, but outside FreePBX you can use Asterisk’ SLA abilities if they suit your needs and abilities and you have enough buttons and patience to program and maintain it (no SecureID card or 1200 baud modem nor 25/50 pair rj21x’s needed anymore though :slight_smile: )


The SLA (Shared Line Appearance/Shared Extension Appearance) your refer here is pretty much what we’re looking to do. Though I am disappointed that transfers appear to not be possible based on what I’m reading. We need that for forwarding calls from a our public line to a given extension/voicemail.

Does FreePBX have a portal for SLA’s.



No portal in FreePBX for SLA’s, it is a PBX

Hi Dicko…

I only want to have one, or two discrete lines appear on multiple phones. I don’t need 5 or 10 line appearances typical of the 1A2 instruments of yore. They would be different groups and serving different functions. Public line would be an all-call/all-ring and 2nd “private” line would ring several operations-only extensions. The 550’s should be suitable in that regards.

The only thing after that should no one answer would be calls automatically picked-up by the auto-attendant.

Thanks all…


Again, you can’t do that readily in FreePBX, you would have to synthesize your “discrete lines” to aliased and convoluted Ring Groups of virtual extensions, but you just can’t currently do your notion of shared lines (i.e. line pickup, hold, transfer a la 1A2 with a hookflash) within FreePBX, it remains a PBX and NOT a key system :wink:

(Many have tried to do what you want over the years , but to my knowledge they have all been ultimately disappointed)

Yeah, it’s not a Key System for sure - LOTS of people are getting rid of their Key Systems, so they can be picked up CHEAP and you could get the functionality you are looking for - you can even use Asterisk to front the system so you can still use VoIP trunks but have line appearances on the desks if you would like.

I won’t try to convince you either way but I will tell you my experience as a Reseller - We were the biggest Samsung dealer in New Mexico in 2004-2007 and we sold a LOT of Key Systems - and then we found freedom with Asterisk and swore we would NEVER go back to a Vendor-Locked-In system of any type - Asterisk being a PBX is an enabling factor, NOT a limiting one.

Shared Line Appearances do work, but if you are a novice and intent on using them, I think you options are as follows (from cheapest to most expensive:

  1. As I suggested before, look at iSymphony - it makes moving calls nice and visual, and the current version is purely web-based so no clients to install and it is Windows/MAC/Linux friendly so no problem there. While it doesn’t put the lines on the phone, the 550 has so few buttons, this might be an advantage.

  2. Contract directly with Digium (Yes they do that, and it’s fairly reasonable) to get the SLA’s working for your setup - they are going to scoff at FreePBX (they are wrong!) and probably try and steer you into Switchvox (their Proprietary Asterisk-Based system) - but if you can get them to help you with the SLA, it will probably work.

  3. Contract with a local expert that has done them. This would not be me, nor do I know anyone - sorry.

  4. Pick up a used Key System and front it with the Asterisk - this will be the most complex option, but you can get exactly what you are looking for.

Good Luck - Asterisk and FreePBX is about Freedom - there are lots of ways to “Skin This Cat” - you just have to pick what works for you - And I have LOTS of customers who want things exactly the way they want them - this is challenging to say the least. I feel your pain.