External Device Use
Cisco recommends the use of good quality external devices, such as speakers, microphones, and headsets that are shielded (screened) against unwanted radio frequency (RF) and audio frequency (AF) signals.
Depending on the quality of these devices and their proximity to other devices, such as mobile phones or
two-way radios, some audio noise may still occur. In these cases, Cisco recommends that you take one or more of the following actions:
the external device away from the source of the RF or AF signals.
the external device cables away from the source of the RF or AF signals.
shielded cables for the external device, or use cables with a better shield and
the length of the external device cable.
ferrites or other such devices on the cables for the external device.
Cisco cannot guarantee the performance of the system because Cisco has no control over the quality of external devices, cables, and connectors. The system performs adequately when suitable devices are attached with good quality cables and connectors.
In European Union countries, use only
external headsets that are fully compliant with the EMC Directive