Cisco Cisco Unified MeetingPlace Audio Server Quick Setup Guide
Troubleshooting Telephone Issues for Cisco Unified MeetingPlace
How to Resolve Problems That Occur During Calls
14
One-Way Audio—User Cannot Be Heard By Other Participants
Problem
User gets one-way audio only. User can hear the voice meeting, but other participants cannot
hear the user.
Solution
Make sure that the user is not muted:
•
Have the user check for a mute button on the phone or video endpoint.
If still in the voice meeting, have the user press #5 on the phone, in case another meeting participant muted the line.
User
"Talk-Off" (Triggering the Pound Key with Your Voice)
Talk-off is the unexpected detection of a digit (often a # key) by voice systems such as Cisco Unified
MeetingPlace.
MeetingPlace.
This is always a statistical possibility due to the imperfect nature of in-band (voice and DTMF sharing
the same voice channel) DTMF tone detection algorithms in any voice device (Cisco Unified
MeetingPlace, PSTN voice gateways). Ideally, in-band DTMF detection in these devices will correctly
detect digits 100% of the time with no false detection of voice as digits. Practically, a small number of
errors -- some voice will be falsely detected as a digit (aka "talk-off") -- are allowed. While most cases
of talk-off cause no reaction in Cisco Unified MeetingPlace during a meeting -- false detection of any
number "1" to "9" or "*" -- and are ignored, false detection of "#" or "0" can cause unexpected Cisco
Unified MeetingPlace behavior.
the same voice channel) DTMF tone detection algorithms in any voice device (Cisco Unified
MeetingPlace, PSTN voice gateways). Ideally, in-band DTMF detection in these devices will correctly
detect digits 100% of the time with no false detection of voice as digits. Practically, a small number of
errors -- some voice will be falsely detected as a digit (aka "talk-off") -- are allowed. While most cases
of talk-off cause no reaction in Cisco Unified MeetingPlace during a meeting -- false detection of any
number "1" to "9" or "*" -- and are ignored, false detection of "#" or "0" can cause unexpected Cisco
Unified MeetingPlace behavior.
The Cisco Unified MeetingPlace in-band DTMF detector meets the requirements of the "Bellcore
Talk-off Test" specifications. The spec allows up to 500 false detections of any digit "0" to "9", "#" and
"*" after the three hour test with real voice snippets. Cisco Unified MeetingPlace measures at 356 false
detects for all these digits with only four false "#" and four false "0" digit detects during this period. So
the Cisco Unified MeetingPlace DTMF detector exceeds the Bellcore spec and changes to the DTMF
detection algorithm are very unlikely.
Talk-off Test" specifications. The spec allows up to 500 false detections of any digit "0" to "9", "#" and
"*" after the three hour test with real voice snippets. Cisco Unified MeetingPlace measures at 356 false
detects for all these digits with only four false "#" and four false "0" digit detects during this period. So
the Cisco Unified MeetingPlace DTMF detector exceeds the Bellcore spec and changes to the DTMF
detection algorithm are very unlikely.
Realistically, though, people are all different. Unfortunately, some voices and speech patterns are more
prone to triggering the DTMF detector than others, so certain users may have a much higher probability
of seeing this problem.
prone to triggering the DTMF detector than others, so certain users may have a much higher probability
of seeing this problem.
Recommendations:
•
For System Administrators: Use out-of-band digit transmission (RFC-2833, KPML) wherever
possible. However, using RFC-2833 may only shift the talk-off problem from the Cisco Unified
MeetingPlace DTMF detector to a voice gateway DTMF detector.
possible. However, using RFC-2833 may only shift the talk-off problem from the Cisco Unified
MeetingPlace DTMF detector to a voice gateway DTMF detector.
•
For End Users: Use the best possible audio connection -- a land-line or a good IP connection with
G.711. In some cases cordless phones may distort speech enough to make a user prone to talk-off.
G.711. In some cases cordless phones may distort speech enough to make a user prone to talk-off.