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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

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