Helmet cable installation
Version 4.3 25 (61)
5.3.1.3 Selection Of The Electret Microphone Capsule
Be sure that the selected electret microphone capsule is RF noise-
resistant type and it fulfils 89 / 336 / EEC EMC directive, because most
of the electret microphones are very sensitive for the RF-noise.
HELMET_MIC+ and HELMET_MIC- inputs are filtered against RF-
noise, but there is no possibility to filter audio frequency noise, which
has been indicated from the RF-signal in microphone capsule.
5.3.2 Speaker Output Interface
Speaker output interface is presented in Figure 3. Speaker output is
balanced type interface. Quiescent voltage in speaker outputs referred
to system ground is about 2.4 V. Speaker output lines have been
protected against EMC and ESD.
Connection with unbalanced accessories (microphone and speaker
use same ground) is not allowed. If common ground will be used,
speaker interface must be equipped with applicable audio balun.
Figure 3 Speaker Output Flowchart
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