i want to build a asterisk pbx system in my office located in a residential area. there are maximum PSTN lines come into my place. i need to have two separate fax machines, 2 different analog phones and several IP phones to connect to this pbx system. i bought two digium TDM cards (one for connecting to PSTN lines, then other for fax machines), can anyone let me know what and how many add-on modules (e.g. FXS or FXO modules and the color to identify each add-on module) for each TDM card i need to buy to achieve this purpose?
FXS (we make them green )provides ring-voltage and battery to analog telephone sets - like handsets and fax machines.
FXO (we make them red) is connected to the PSTN.