First a suggestion- if you dont have much experience with unix/linux or *, consider hiring somebody to set it up. It will probably go much smoother and be more reliable… I know the first few times I wrote * dialplans they were a total mess. both drwho and baconbuttie have been around here for a while and I’m sure they can get you set up very nicely and with great ease/speed.
Also FWIW this is an example setup. The real trick is the integration, making this work. You can’t just buy phones and plug them in…
Anyway:
First you dont need a static ip. You can use a dynamic dns service which will work pretty well. FXO card plugs into a LINE, FXS card plugs into a PHONE and provides the phone with dialtone. FXO/FXS are only needed for dealing with POTS analog phones/lines. Asterisk uses your system’s network card for VoIP.
Japan Office
Router for DSL with quality of service control
Server running Linux and Asterisk
Digium TDMxx card (one fxo) for analog line
1x BRI (isdn) card, there’s a few of them around.
for staff- VoIP telephones of your choice (I recommend AAstra or SNOM hardware).
Philippines office
Router with QoS control
Server running Linux and Asterisk
8x softphone (xten eyebeam, sjphone, idefisk, etc) for telemarketers. Uses existing computer and a headset. Cheaper.
10x VoIP telephone of your choice for staff.
All VoIP numbers would register to * box in Japan, which would allow reinvites to Philippines. There would also be an IAX2 trunk for extension dialed calls. Calls ring * box in Japan, get IVR etc, then get forwarded to philipines if they have to talk to a rep down there. 4 digit extensions would be assigned to all agents and users, anybody could call anybody else with 4 digits regardless of what office they are in.
Another thing to consider- VoIP sort of abandons the concept of a ‘line’. IE, you do not need separate accounts for each user. There are many VoIP companies that will sell/port you a DID (phone number), over which any number of concurrant calls can be handled. You can also dial out and be charged a low fee per minute per call, in the USA its usually 1-3us cents per minute per call. This may or may not save you money.
Also, as I said before, this is easy to talk about, but hard to do. Asterisk is like a tub of Legos, you can make something cool out of it but you have to know how. If your business is going to depend on it, consider hiring a pro to set it up right.
Hope that helps!