Bose A20 Details on making the connections, Helicopter U174 connection diagram, Pin number, Color

INSTALLATION

Helicopter (U174) connection diagram

WHT/BLU 6 MIC LO

	WHT	5	MIC HI
	BLU
		4	COMM R
	WHT
		3	COMM L
	BLK
		2	GND
10-32 RED
		1	V+IN
V DC	1/2A
Existing single 4-
	prong jack
Existing wiring to			Barrel
helicopter intercom/
			(audio gnd)
audio panel

Note: Barrel ground (gnd) refers to aircraft grounds.

Details on making the connections

The pinouts for the optional installed connector are detailed in the table below:

Pin number	Color	Purpose
1	Red	V+IN: Headset power (10-32 VDC). Use a 1/4 amp fuse or
		a 1/2 amp circuit breaker.
2	Black	GND: System ground. Connect to the existing audio ground.
3	White	COMM L: Phone communication: Left.
4	Blue	COMM R: Phone communication: Right.

Note: For stereo operation, connect the left and right channels to their respective positions. For monaural operation, connect pins 3 and 4 together, and to the tip of the existing phone jack.

5	White	MIC HI: Microphone/Hi-audio. Connect to the portion of the
		existing microphone jack that corresponds to the ring
		position of a headset microphone plug. Do not connect to
		the tip (PTT) segment.
6	White/	MIC LO: Microphone/Lo-ground. Connect to the portion of
	Blue	the microphone jack that corresponds to the barrel position
		of a headset microphone plug.

Note: If the microphone works on radio transmit but not through the intercom, check pin 6. It may be incorrectly wired to the PTT segment of the microphone jack.

Comm Shield	Black	Shield from Comm L and Comm R wire pair.
Mic Shield	Black	Shield from Mic Hi and Mic Lo wire pair.

Note: The wires connecting pins 3 and 4 and pins 5 and 6 are shielded, twisted pairs with a black wire shield termination exiting each pair. If the existing wiring is not shielded, connect the shields to the existing audio wiring shields, or connect the shield from Comm L and Comm R wire pair to audio ground.

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