Ovislink OV804WV User Manual page 189

enables you to place and receive calls over the Internet using a
standard telephone set connected to SIP Proxy or other
devices which have/include the same functions as SIP Proxy.
With proper dial-plan setting, calls on DSL Router may be
routed to PSTN network or VoIP network, depending on what
digits you dial.
DSL Router provides 2 FXS interfaces and 1 FXO interface.
FXO is connected to telephone line, through which you dial up
to Internet. Normally the telephone line is multiplexed with both
telephone signal and data signal. If not filtered out by a splitter
before entering FXO interface, the incoming PSTN calls are
routed to FXS-connected analog phone or other VoIP user. You
can use up to 2 analog phones, each connected to one FXS
interface. The two are called endpoint, and act as an
independent role as IP phones.
4.6.1.1 SIP Entities
DSL router's VoIP solution use session initiation protocol (SIP)
to create, modify, and terminate calls. SIP is an Internet
application-layer protocol that runs in user agent and server
systems for controlling multimedia sessions between users,
who may move from one location to another, and use terminal
devices with various media capabilities. For more details about
SIP, please see RFC3261.
In order to form concepts of SIP, terminology of SIP is
displayed as below.
POTS: plain old telephone service. The traditional telephones
we use in home are POTS.
User agent (UA): it includes UA client (UAC) and UA server
(UAS). UAC originates calls, and UAS listens for incoming calls.
DSL router can serve as UAS and UAC.
SIP Proxy: routes call requests. If we create a call to invite our
friends or relatives through SIP, our call is routed through SIP
Proxy, for only it knows your friends' or relative POTS' position.
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