User's Manual

Cisco High-Density Analog Voice and Fax Network Module
Configuration Tasks
14
Cisco IOS Release 12.2(2)XT and 12.2(8)T
Configuring Disconnect Supervision Commands
PBX and PSTN switches use several different methods to indicate that a call should be disconnected
because one or both parties have hung up. The commands in this section are used to configure the router
to recognize the type of signaling in use by the PBX or PSTN switch connected to the voice port. These
methods include the following:
• Battery reversal disconnect
• Battery denial disconnect
• Supervisory tone disconnect (STD)
Battery reversal occurs when the connected switch changes the polarity of the line to indicate changes
in call state (such as off-hook or, in this case, call disconnect). This is the signaling looked for when the
battery reversal command is enabled on the voice port, which is the default configuration.
Battery denial (sometimes called power denial) occurs when the connected switch provides a short
(approximately 600 ms) interruption of line power to indicate a change in call state. This is the signaling
looked for when the supervisory disconnect command is enabled on the voice port, which is the default
configuration.
Supervisory tone disconnect occurs when the connected switch provides a special tone to indicate a
change in call state. Some PBXs and PSTN CO switches provide a 600-millisecond interruption of line
power as a supervisory disconnect, and others provide supervisory tone disconnect (STD). This is the
signal that the router is looking for when the no supervisory disconnect command is configured on the
voice port.
Note In some circumstances, you can use the FXO Disconnect Supervision feature to enable analog FXO
ports to monitor call progress tones for disconnect supervision that are returned from a PBX or from
the PSTN. For more information, see the “Configuring FXO Supervisory Disconnect Tone
Commands” section on page 16.