Installation manual

User & Installation manual
VHF- Communication Transceiver
Doc.-Nr:
DE-3000-800100e
KRT2 & KRT 2A
Revision 4.0
38 of 45
5.10. Microphone general
The correct setting of the MIC and VOX values is of great importance for
Intercom system (see 3.4.3. VOX Intercom Voice Trigger Level and
3.4.10. MIC Setup).
The VOX intercom voice trigger level must be set to such a value that the
intercom system is activated when speaking at a normal voice level into
the microphone. It shall not be triggered by normal cockpit noise.
When there is extreme cockpit noise or there are uncompensated
microphones VOX can be deactivated with VOX=01 to enable manual
intercom operation.
The manual intercom operation is activated with one or two separate,
parallel connected, optional intercom switches. These switches are not the
PTT switches. The intercom switches connect pin12 (intercom) with GND
(pin1-and-9).
Communication with the VOX system requires pin 12 to be connected to
GND by means of one or two intercom switches.
The KRT2 unit transmits only when a PTT switch is pressed.
Cockpit noise suppression is only possible with differential microphones
used in modern headsets. Normal Electret microphones are not suitable.
5.11. Post-Installation Check
A certified maintenance shop must verify the proper
operation of the VHF transceiver.
A complete check of all airplane systems is required to certify that the new
wiring is not causing any malfunction.
The standing wave ratio must be less than 3:1.