User manual

Release 1.01 Digium, Inc. Page 37
Chapter 4
FXS and FXO Explained
Identification
There are multiple standard configurations in which the TDM800P card
may be purchased. Each configuration consists of one to four FXS and/or
FXO modules. These modules are identified by their color.
 FXS - Foreign Exchange Station (Green Modules)
 FXO - Foreign Exchange Office (Red Modules)
This chapter provides an in-depth review of the two module types and
their uses within your Asterisk server.
Note: Only qualified service personnel should install the card. Users
should not attempt to perform this function themselves.
FXS Module
The FXS module allows the TDM800P card to initiate and send ringing
voltage to an FXO device such as an analog telephone.
FXO Module
The FXO module allows the TDM800P card to terminate analog
telephone lines (POTS).
Because of the modular design, you can activate additional ports at any
time with more FXS or FXO daughter cards. The FXO module passes all
the call features any standard analog telephone line will support. The
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