Can anyone describe how can we use the FXO relay function on SRP521W?
Does it relay PSTN incoming calls to one of the FXS ports all the time, or is it configurable?
What about connection between FXS and FXO relay when we have power failure, does PSTN backup to one of the ports like SPA3102 does?
Sorry for the late response:
A relay switch is incorporated in to the SRP520, such that it directly connects the FXO port and the first FXS port when:
Therefore, when the device is actively registered to a SIP telephony service, the FXO port is disconnected and otherwise unused. Because the FXO port is only ever used to directly connect a phone line and a handset/fax connected to the first FXS port, there is no configuration required for it.
It is not possible to route calls to the FXO port on the SRP520.
Correct - the FXO port is not really active in any way - think of it as a basic pair of copper wires that connect phone port 1 to the jack in the wall in failure conditions (i.e. equivalent to unplugging the phone and plugging it directly in to the wall jack)