Weed Eater 2600 manual Telephony Signaling Interfaces, FXS and FXO Interfaces

Cisco High-Density Analog Voice and Fax Network Module

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 on-hook status, ringing, and line seizure.

The router’s voice-port hardware and software must be configured to transmit and receive the same type of signaling being used by the device with which they are interfacing so that calls can be exchanged smoothly between the packet network and the circuit-switched network.

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 end-user telephony equipment, such as a telephone or fax machine. Figure 2 shows an FXS connection to a telephone and an FXO connection to the PSTN at the far side of a WAN; this might be a telephone at a local office going over a WAN to a router at headquarters that connects to the PSTN.

Figure 1	FXS Signaling Interfaces
	Voice port	Serial or	Serial or Voice port
	1/0/0	Ethernet port	Ethernet port		1/0/0
			WAN
	FXS	V		V	FXS

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Figure 2	FXS and FXO Signaling Interfaces
	Voice port	Serial or		Serial or Voice port
	1/0/0	Ethernet port		Ethernet port		1/0/0
			WAN				PSTN
	FXS	V			V	FXO

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FXS and FXO Interfaces

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. 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.

Cisco IOS Release 12.2(2)XT and 12.2(8)T

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