I´m in the first year of my apprenticeship and i´m going to be a IT-Specialist for system integration.
I´m from germany, so please be patient with me and my english skills
At the moment I got the task to set up a Server with Asterisk wich is connected to 2 IP-phones.
Is it possible to log the calls for later analysis? (in .mp3 format for example)
What are the hardware requirements? (I read a lot “It Depends on the number of Calls” but no exact Information for just 1 call at a time)
For your requirement (2 calls) you could use any second hand computer you could find in the “spare room” and on which you could install Asterisk.
You could install Asterisk even from a distro CD like Asterisk-now or using the normal way of trying and learning -> installing Linux (like Centos) + compiling Asterisk (or use the OS specific application installation tool - like yum in Centos) + using the dialplan commands in order to understand how Asterisk works.
Regarding keeping the records of the calls - I would suggest to use WAV extension instead of mp3 - as this is directly supported. For mp3 you have to use an offline tool (like lame) - some details could be found here (from voip-info.org)
Given there is no point in having a PABX for only two phones, I assume that you have some connection to the outside world. You may or may not need special hardware, depending on the nature of that connection, and possibly your current network arrangements. All common SIP phones work with Asterisk. You really need to read the book to which you were referred.
For running simple tasks, i.e. hosting an Asterisk PBX system, my preference is a Linux embedded system. The reasons are simple, no noise, and operational cost is at a minimal.
I have a FON2100 WiFi router that has been flashed with an OpenWRT firmware and turned into a Linux embedded system to host my Asterisk PBX system. Its AC/DC adapter is rated 5VDC @2Amps (10Watts). It has a limited 8/16MB Flash/RAM capacity. So, logging activities have been disabled.
Also, I have another Asterisk PBX system hosted on a long discontinue Netgear WGT634U WiFi router flashed with an OpenWRT firmware. Its AC/DC adapter is rated 12VDC @1Amp (12Watts). It has no problem to log I/O calls on a USB memory stick plugged into its USB port. It even can e-mail out voicemails. If I had an SMS capable phone, I am sure it can also do SMS. So, depending on what you want to achieve, a simple hardware, like a long discontinue Netgear WGT634U WiFi router, can do a lot for a much less operational cost in electricity than a full-blown computer (200+ Watts?) to waste a lot of electricity.
I think he wants a development configuration, for part time use, not an embedded production system. As such he really wants something as close to the standard implementation as possible.
Same way as any other IP over ethernet device. For xBaseT, you will need at least a hub (although, you could use the PC as a router, if you had two ethernet interfaces on it).
So, depending on what you want to achieve, a simple hardware, like a long discontinue Netgear