Asterisk-Stuff (PBX)

Note: This article is dated to 2018 since my company no longer exists and the pbx will not be maintained any more (at least not by myself).

In late 2010 I introduced an Asterisk-PBX in my company (with a total of about 35 phones) to replace our old Siemens Hicom. It is connected to the world via three ISDN-lines (really, no VOIP-lines until now), has 12 internal ISDN-busses (we need them for modem- and faxconnections) and mostly Grandstream GXP2110-phones.
For the ISDN-lines, we use octoBRI-cards from Junghanns.

On this page I would like to report about my problems and solutions. I must express that I'm no asterisk-professional (who could solve some of my problems probably much faster and better than I did). I just found the thought of a free PBX and its potential to connect everyone for free very exciting (we have lots of expensive connections to far east), played around for some time and now have the responsibility for a 24/7 working PBX.

About for free: meanwhile I managed to connect my Fritz!Box at home via VPN as a phone to Asterisk so I can call everyone at no costs as if I was in the company. The advantage of this is, the Fritz could be anywhere out in the world and thanks to VPN the calls are absolutely resistant to monitoring from anyone!


Which phones should I buy? This was my first problem. Well, you should not buy lots of different brands and types of phones. A major part of the time necessary to introduce a VOIP-PBX is the programming of the phones, writing a user-documentation on your intranet, fixing (or limiting...) problems and so on. Every phone is different. If you have only one type of phone, you can make use of configuration tools and files and set up a phone in less than 10 minutes (including the time for necessary reboots...) but the first one will take two days easily! You would not save money if you buy 10 cheap phones for the 'lower class' and need two days to set them up!


I found only few information about DECT and VOIP. At last, I chose Aastra DECT-bases what later proved a good one. We have two DECT-bases and everything works perfect. Seamless handover included. The bases are smart, robust and do not crash. But you need time. The Aastra-bases are booting their firmware from a TFTP-Server which you have to set up first. And your DHCP has to tell them where to find it.
One base (RFP, radio fixed part) is chosen to be the master. Only this one has a WEB-interface on which you can setup the PPs (portable parts, the DECT-phones themselfs). Handover is handled internally without any need to setup something in asterisk's configuration. Every DECT-phone has an entry in the sip.conf and that's all!
The bases must be able to 'see' each other over the air. This is because the Phones use time slots in the band of the base which have to be exactly synchronous with every slave base. If they have no radio contact, the slave will never become active.
The Aastra-manual is bad, really bad. It is written from DECT-gurus for DECT-gurus but definitely not for me. They say, the master base can administer 512 Phones but I still do not know how many phones can be booked in at a single base and how many can talk simultaneously. If you encounter a limit here, you probably have to buy another base, even if it would be only a few meters away.
A major fault is to prepare all phones and then try to connect them to the base. It does not look for the pin. It just tries to connect the phone it thinks it is the first. Just complete each phone one by one and it will work. It costed me hours to learn that.


I bought three types of SIP-phones, two Elmeg IP290 (similar to SNOM 190), an Aastra 6739i and two Grandstream GXP2010 for testing. I liked the Grandstream because of its 18 programmable keys for BLF (Busy Lamp Field) or speed-dial. Some developers seem to think keys are expensive, Grandstream proves they are not!
I like lots of keys. You can always program one with a sign please do not press this button again :-)
The Elmeg is more expensive than the Grandstream and has fewer keys so I decided for Grandstream. The Aastra is definitely better (looks better, feels better, is much more intuitive to handle and it does not crash) but it costs more than three of the Grandstreams so the choice was clear (at least after I talked to the management).
Unfortunately, the 2010 is no longer available and has been replaced by the 2110 so I ordered 24 of them. The Firmware seemed to be done only half. They've caused lots of problems like crashes when numbers in the phone book exceed 10 digits and users not being able to program keys on the extension table. The latest firmware (which has been revoked by Grandstream) tended to crash several times a day at our reception (they obviously did not expect that anyone would program more than 7 blf-keys) and a reset key would have been on the wishlist for the future...
In version which has been released after more than a month of silence these problems seemed to be solved. I can't believe that these two major problems - blf and 10-digit - were such a hard thing. If this was my work I surely released a quickfix overnight...
Also, Grandstream is an American company and they seem not to take much care for the international market. The 2010 not even was aware of charsets and could not display German umlauts. The 2110 can even display weather-forecasts but only for American ZIP-codes (at least, the usage of others is not documented). It seems to be a curse of modern times that products are sold if they are half ready.


The Aastra has a touchscreen, labeling is therefore not necessary. That's the advantage if you spend €350 for a single phone.
The Template for the GXP2010/2110 you can download from the Grandstream website is poor. It is a simple PDF-table you must fill out with a pen. I made a template for MS-Word (also usable with open office) and I like to provide it here for download. Maybe it is not really beautiful but you can fill it out on your PC, color the background at will and what's best, the table outline fits into the phone's keypad. Just try it! It's a little fun after all that work!