I have an Asterisk at home running on a little PC Engines ALIX board (purchased from NiceGear). Phones used are (in no particular order) Panasonic, Snom, Polycom, Yealink and Grandstream. The main connection to the PSTN is a SIP trunk to 2talk over a Vodafone HFC Cable Internet connection (possibly changing to a UFB fibre connection this year sometime). For redundancy I have 2talk fail over incoming calls to a cell phone number if my PBX is unreachable (i.e. Internet issue). It doesn’t go to a cellphone though, it goes to a cheap GSM SIP CTU which sends the call into the PBX, ringing all the phones just like normal. The CTU and the “PBX” are run off the same UPS as the PoE switch powering the phones so when the phones stop working during a power cut so does the PBX and the CTU. To allow for this I have call forwarding set up on the CTU’s phone account to forward calls through to an actual cellphone. So when there’s a power cut, longer than the UPS can handle, calls are forwarded to the CTU which is unreachable so the cell network forwards the call to one of our cellphones. Normally I would use 2degrees for a SIM for the CTU, in this case it was my only choice. The CTU is a 2G GSM device, Spark doesn’t have a 2G network, only a 3G network so they are out leaving just Vodafone and 2degrees. On prepay Vodafone only allows a call forwarding destination of their voicemail service whereas 2degrees has no such restriction so they were my only choice (as well as my preferred choice). Seems to work fine, I’ve just got to remember to top up the CTU’s SIM $20/year to keep it active.
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