Linking two HT503s together


I wan’t to link two old analogue PBXs in different locations by having a HT503 in each location. Can the HT503s be programmed to connect to each other directly (Over the internet) with out the need of a SIP provider?
Also does the FXS port accept old pulse dialing?


If you want use FXS port, why you buy 503 ?
Simple 1 fxs port do it. and yes it will work but port need to be forwarded if it is not Intranet.


Thank you for prompt response.
I want to be able to dial in both directions from either PBX into the other PBX.
I was thinking that on each PBX I would connect one of the spare PSTN ports to the FXS of the HT503, and one of the spare extension ports to the FXO port.
Doing the same at the other site, and then connecting the two HT503s over the internet.
What programming is needed to make them talk to each other? Do I leave the SIP server entry blank, or enter the other ends IP addr? What about user name?
I appreciate that both HT503s will be behind firewalls so will need port forwarding of port 5060.


5060 + 5062 (for FXO), also 5004 RTP.
SIp server other device with port.
Turn off register.

I’m not sure why you want use FXO with extension but this will rather likely work strange.
You need call extension first then it connect t to 503 then forward to other PBX, but you need stop call on FXO and wait for user put number he want dial.