Specifications

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Cisco 1751 Router Software Configuration Guide
OL-1070-01
The voice ports support three basic voice signaling types:
• FXS—The foreign exchange station interface uses a standard RJ-11 modular telephone cable to
connect directly to a standard telephone, fax machine, PBXs, or similar device, and supplies ring,
voltage, and dial tone to the station.
• FXO—The foreign exchange office interface uses a RJ-11 modular telephone cable to connect local
calls to a PSTN central office or to PBX that does not support E&M signaling. This interface is used
for off-premise extension applications.
• E&M—The E&M interface uses a RJ-45 telephone cable to connect remote calls from an IP
network to PBX trunk lines (tie lines) for local distribution. It is a signaling technique for two-wire
and four-wire telephone and trunk interfaces.
Configure FXS or FXO Voice Ports
Under most circumstances, the default voice-port values are adequate to configure FXS and FXO ports
to transport voice data over your existing IP network. However, if you need to change the default
configuration for these voice ports, use the following commands beginning in privileged EXEC mode:
Command
Required or
Optional Task
Step 1
configure terminal Required Enter the global configuration mode.
Step 2
voice-port slot-number/port Required Identify the voice port you want to
configure and enter the voice port
configuration mode.
Step 3
dial-type {dtmf | pulse} Required (For FXO ports only) Select the
appropriate dial type for out-dialing.
Step 4
signal {loop-start |
ground-start}
Required Select the appropriate signal type for this
interface.
Step 5
cptone country Required Select the appropriate voice call progress
tone for this interface.
The default for this command is us. For a
list of supported countries, refer to
Chapter 4, “VoIP Commands.”
Step 6
ring frequency {25 | 50} Required (For FXS ports only) Select the ring
frequency (in Hz) specific to the
equipment attached to this voice port and
appropriate to the country you are in.
Step 7
ring number number Required (For FXO ports only) Specify the
maximum number of rings before
answering a call.
Step 8
connection plar string Optional Specify the private line auto ringdown
(PLAR) connection if this voice port is
used for a PLAR connection. The string
value specifies the destination telephone
number.