Cisco
Feature Overview
Telephony Signaling Interfaces
Voice ports on routers and access servers physically connect the router or access server to telephony devices such as telephones, fax machines, PBXs, and (PSTN) central office (CO) switches. These devices may use any of several types of signaling interfaces to generate information about
The router’s
The signaling interfaces discussed in this document include foreign exchange office (FXO), and foreign exchange station (FXS), which are types of analog interfaces. It is important to know which signaling method the telephony side of the connection is using and to match the router configuration and voice interface hardware to that signaling method.
The next three illustrations show how the different signaling interfaces are associated with different uses of voice ports. In Figure 1, FXS signaling is used for
Figure 1 | FXS Signaling Interfaces |
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| Voice port | Serial or | Serial or Voice port | |||||
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| 1/0/0 | Ethernet port | Ethernet port | 1/0/0 | ||||
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| FXS | V |
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Figure 2 | FXS and FXO Signaling Interfaces |
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| Voice port | Serial or | Serial or Voice port | ||||||
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| 1/0/0 | Ethernet port | Ethernet port | 1/0/0 | |||||
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| PSTN |
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| FXS | V |
| V | FXO | ||||
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FXS and FXO Interfaces
An FXS interface connects the router or access server to
An FXO interface is used for trunk, or tie line, connections to a PSTN CO or to a PBX. This interface is of value for
Cisco IOS Release 12.2(2)XT and 12.2(8)T
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