Cisco Unity

Document ID: 13933

Contents

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
Collisions
      Troubleshoot a Collision
Dial Tone Detection
Related Information

Introduction

This document discusses collisions and dial tone detection in Cisco Unity.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on the Cisco Unity for Exchange Unified Messaging.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

For more information on document conventions, refer to the Cisco Technical Tips Conventions.

Collisions

A collision occurs when a call is outgoing on a port at the same time that an incoming call is answered. This is similar to what happens when you pick up the phone to make a call and do not hear a dial tone. You say hello and find that someone who had just called you is on the line. In Cisco Unity, the incoming call always takes precedence over the outgoing call.

A caller does not notice anything as a result of the collision. To avoid a collision, Cisco Unity verifies that the switch provides dial tone before it does an out dial. If no dial tone is detected, Cisco Unity assumes that an incoming call was delivered as the same time the port went off-hook to dial. The call is routed to the main greeting and collision is displayed on the port screen. If the dial-out is message delivery or Message Waiting Indicator (MWI), it is considered failed and attempted at least once on another port before using the retry failure setting.

If a line is not plugged into the voice port, a collision is reported when a dial-out is attempted. The Arbiter diagnostic 13 Ports reports this as a collision.

Troubleshoot a Collision

To troubleshoot a collision:

1. Verify a line is plugged into the voice port.

2. Verify that the switch sends a strong, consistent dial tone by monitoring the line with a butt-set and following the progress of the call to identify where the breakdown is.

   The correct progress of the dial out is:

   1. Hook flash.

   2. Immediate strong dial tone.

   3. Digits dialed.

   4. Hook flash to connect the lines.

   5. Cisco Unity terminates the call.

   If the switch does not send a dial tone, it is possible to disable the check for dial tone on an out dial. This should only be done on the ports used for MWI and pager notification, to avoid the possibility of a true collision. Disabling this parameter also disables Unity's ability to monitor call progress. If Collision Disabled is set to 1, all notification attempts are considered a success whether the call is answered, ring-no-answer, busy or if no line is plugged into the voice port. This can result in many people never getting notification calls unless they happen to answer on the first attempt. Only change this setting as a last resort.

Dial Tone Detection

Dial tone detection on a dialout is a system wide parameter, which is enabled by default. It is located in this registry key:

• Registry: Software/Active Voice/MIU/1.0/Initialization

• Parameter: Collisions Disabled

  • 0 (default): Dial tone detection when going off-hook

  • 1: No dial tone detection when going off-hook

Related Information

• Voice Technology Support
• Voice and Unified Communications Product Support
• Recommended Reading: Troubleshooting Cisco IP Telephony
• Technical Support - Cisco Systems