Check the DP5000 user guide for more, but this may give you a start:
"The DP5130-FSDL has a powerful integrated full duplex speakerphone that provides
bi-directional voice transmission, allowing simultaneous talk. The microphone is
located on the front right side of the telephone, so all objects need to be kept well clear
of that area to ensure there are no reflections that might generate an echo or other
feedback. In a full duplex speakerphone environment, a number of conditions
including room acoustics, network conditions, or the other party’s equipment can
induce echo, a short silence, or clipped speech, so it is important to use the following
recommendations for optimal performance.
Recommended Environment for Optimal Performance
• Keep objects, for example; books, equipment or walls, away from the front and
sides of the telephone.
• Keep telephone away from noise sources (e.g. PC fan).
• For small, enclosed office environments that have acoustical reflection, it may be
necessary to select the lower speakerphone/microphone sensitivity setting (as
shown above).
• The DP5130-FSDL is not recommended for very small rooms, which tend to have
higher acoustical reflection and can result in echo or feedback. For this room
environment, please consider the DP5130-SDL model (half duplex speakerphone).
• When using a SIP Trunk backbone Toshiba recommends the IP5131-SDL model,
which is optimized for a full IP environment.
Key Considerations for Better Call Quality
• The powerful built-in echo canceller is constantly adjusting to its environment,
providing optimal performance. For the first few seconds of a call, only one side
should speak at a time as the echo canceller optimizes for its environment.
• For best performance, users should speak in front or slightly to the side of the
telephone.
• In a full duplex environment, it is important that both sides speak at similar voice
volume levels. If you hear clipped speech on your side, please speaker louder and/
or move closer to the microphone so that your speech is properly identified by the
echo canceller.
If you hear clipped speech from the other side, please ask them to speak louder
and/or move closer to the microphone. The DP5000 Series provides a wide range
of volume steps, so you can also lower your volume setting 3 to 7 steps to better
match the voice levels.
• The echo canceller is constantly optimizing, so it is important not to move the
telephone while in use. Furthermore, do not move paper or other objects near the
microphone area during the call, which could generate a loud noise or cause an
echo to be transmitted to the other side.
• Should an echo occur, simply pause a moment to allow the echo canceller to readjust.
Continue to follow the steps above for better call quality"
