User guide

4.5.3 PSTN interface cards
If you want to route calls from your VoIP terminals to the traditional telephone network (PSTN) you
need to include dedicated hardware in the PBX for that purpose. A modular solution for Asterisk that
allows you to connect analogue lines and phones is a PCI card from Digium: TDM400P wildcard.
The card is known as a “TDM wildcard” because it provides the possibility of inserting any combination
of FXO or FXS modules into 4 ports. This means that the same PCI card can be used to connect four
incoming lines (4 FXO modules), or two incoming lines (2 FXO) and two analogue phones (2 FXS
modules), etc.
To get you started, consider buying the TDM400P with one FXO module (to connect one phone line)
and one FXS (to connect an analogue phone). If you need to expand in the future, you can always buy
extra modules.
Image 3: A 4 port TDM400 wildcard. Two ports (Port 1: FXO, Port 2: FXS) are occupied while the remaining (Port
3 and 4) are idle for future use.
4.5.4 Analogue Telephone Adaptors
An Analogue Telephone Adaptor (ATA) or a Telephone Adaptor (TA) connects a standard analogue
telephone to a VoIP network. An ATA has an RJ-11 (phone jack) and an RJ-45 (Ethernet) jack. An ATA
acts like an FXS adaptor, talking analogue with the phone and digital with the VoIP network.
Page 16 TRICALCAR | www.wilac.net/tricalcar – Version: February 2008