My guess is that connecting an FXS port to the CO would do either nothing (no Off Hook detection) or perhaps Busy out the CO circuit (permanent Off Hook). As a Station card the FXS will not have the ability to communicate properly with the Central Office Exchange :)
Analog telephony signaling, the original signaling protocol, provides the method for connecting or disconnecting calls on analog trunks. By using direct current (DC) over two-wire or four-wire circuits to signal on-hook and off-hook conditions, each analog trunk connects analog endpoints or devices such as a PBX or analog phone.
To provide connections to legacy analog central offices and PBXs, Cisco CallManager uses analog signaling protocols over analog trunks that connect voice gateways to analog endpoints and devices . Cisco CallManager supports these types of analog trunk interfaces:
Foreign Exchange Office (FXO) Analog trunks that connect a gateway to a central office (CO) or private branch exchange (PBX).
Foreign Exchange Station (FXS) Analog trunks that connect a gateway to plain old telephone service (POTS) device such as analog phones, fax machines, and legacy voice-mail systems.
An FXS interface connects the router or access server to end-user equipment such as telephones, fax machines, or modems. The FXS interface supplies ring, voltage, and dial tone to the station and includes an RJ-11 connector for basic telephone equipment, keysets, and PBXs.
An FXO interface is used for trunk, or tie line, connections to a PSTN CO or to a PBX that does not support E&M signaling (when local telecommunications authority permits). This interface is of value for off-premise station applications. A standard RJ-11 modular telephone cable connects the FXO voice interface card to the PSTN or PBX through a telephone wall outlet.
FXO and FXS interfaces indicate on-hook or off-hook status and the seizure of telephone lines by one of two access signaling methods: loop start or ground start. The type of access signaling is determined by the type of service from the CO; standard home telephone lines use loop start, but business telephones can order ground start lines instead.
Hi Rob, thanks for the info. The problem we have is a remote location of our has no FXO ports and has connected FXS ports to the CO there. They claim that it all works, but we are seeing problems with duplicate DTMF digits being generated across those lines. Is it possible that the cause of the duplication DTMF digits is b/c of the incorrect FXS-CO configuration?
Wow! Are they sure this is a FXS port? I can't ever see this working and I guess it really isn't from you explanation. These Duplicate DTMF Digits are usually due to a problem with the Inter-Digit Timers between the CO and Router. I guess if this really is an FXS port maybe this would explain the problem.
I'm not sure what else I can tell you my friend :(
The situation was actually a Panasonic PBX that had FXO to a Cisco Router gateway and connections to their LEC that they told me were FXS. After prying deeper into it, it turned out that they were mistaken, and FXO ports were actually being used.
SIP traces provide key information in troubleshooting SIP Trunks, SIP
endpoints and other SIP related issues. Even though these traces are in
clear text, these texts can be gibberish unless you understand fully
what they mean. This document attempts to br...
Please find the attached HTML document, download and open it on your PC.
This provides an easy to use form where you simply answer a few
questions and it will render the proper jabber-config.xml file for you
to copy/paste. There is built in logic to verif...
CUCM Database Replication is an area in which Cisco customers and
partners have asked for more in-depth training in being able to properly
assess a replication problem and potentially resolve an issue without
involving TAC. This document discusses the bas...