FXO vs. FXS clarity please

[DManigo]

I have Cisco 1751-v4 router. I'm gathering as much information as I can regarding configuring the router for VoIP.However, I am confused.

"FXO interfaces provide a gateway from the VoIP network to the analog PSTN or to a PBX that does not support E&M signaling so that users can reach telephones and fax machines outside the VoIP network","To create a POTS dial peer for an FXO interface, the destination pattern refers to outgoing calls, and you can include wildcards in it because the PSTN performs the switching."

Question:
Is the function of the PSTN replaced with the VoIP providers SIP?
Will the connection with the providers SIP server provide dialtone?

TIA

 

[ADB100]

You connect an FXO Interface direct to a PSTN line or an extension off the PABX - Foreign eXchange Office.
With an FXS Interface you connect an analogue phone direct to the router - Foreign eXcahnge Station.

Generally you would use an FXO interface as a break-out to the PSTN or to extend PABX Extensions through your IP Network. FXS Interfaces can be used at a remote office to connect analogue phones direct to the router. The voice is then sent over IP through the routed IP network to either terminate on other FXS interfaces (Phone to Phone), to FXO Interfaces (Phone to PSTN Line/Extension) or to IP Phones or other IP devices (Phone to IP Phone).

HTH

Andy

Andy