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New Member

FXS vs FXO for PBX Integration

We're tying a 3640 w/ FXS interfaces to a Siemens/Rolm 9200's FXOs. We need assistance with properly passing digits back and forth. I get digits from the Rolm as expected, but the Rolm won't take digits from the 3640.

Cisco Employee

Re: FXS vs FXO for PBX Integration

The FXS interface won't send digits towards a PBX.

FXS Sends dial-rone & ring & rcv's digits.

FXO Sends ditigs & rcv's dial-tone & ring.

If you want to use 1 port for communication in both directions then you need an E&M interface on the gateway & PBX.


New Member

Re: FXS vs FXO for PBX Integration

I guess that's obvious enough. I thought there'd be a way in IOS to support passing digits both ways.

Okay then, a few questions. Is FXS to FXS and option, whereas both ports would receive digits? And are E&Ms on a VG200 supported (via H323 registration in the CM)?

I'll look for sample configs on this but would appreciate feedback.