DIY

When working with these PBX-systems, a complete new world has opened. The possibilities are endless, but there are also some practical limitations.

• The system should work with the already existing PSTN
• The available DECT-telephones must be used.
• Costs should be low.
• Nothing must change for the enduser in order to make a normal call, or to receive one.
• Calling must still be possible when the server or internet is offline.

Setup with Voice-modem

• A $10 Linux Answering machine - An Asterisk PBX system using an Intel 537 voice-modem.
• A list of hardware-options for use with Asterisk - Given options are a bit Digium-biased.

Note: There are problems with intel 537EP & FA82537EP chipsets, but the 537PU & 537PG should work.

No-go for the Sweex CA000022 (537EP chip)

Possible problems

• Will the connection between the line- and phone-jack be made when the server is offline?
• Is it possible to make the (DECT-)phones ring when someone is calling you via the PBX?
  • If not, what is needed (60V power-supply?) to make it work?
• Will it work with the Dutch telephony system?
• Is it possible to make Asterisk signal the call and operate upon the caller-id, or the number of rings before Asterisk interveines?
• will the modem block incomming caller-id info when the incomming phoneline goes through the modem?
• Is it only possible to use the PBX as an extra telephone, not as a gateway?
• will you need an extra DSL-line-filter to filter out all ADSL-signals (all > 5 kHz) before digitizing the call?
• Is the available PC capable of handling thousands of interrupts per second for the call, without slowing down other applications?
  • Does the Linux-kernel have to be optimized for faster taskswitching? (Realtime-optimalisations, 2.6 kernel, etc.)

Common Of The Shelf components

• Targa SIP/VoIP phone sold at the Lidl (26-2-2007) - A €70 euro wireless SIP-phone. (Manual)