Bose A20 User Manual

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Power and cable variations

The Bose® A20® Aviation Headset is available for purchase in different standard aircraft connector options, including:

Battery powered options

Dual powered options

Operate with battery power only

Operate with either aircraft or battery power


No battery needed when connected to aircraft power



Dual G/A








*An adapter is available from Bose to convert a 6-pinconnector to a dual G/A or U174 plug for additional connection flexibility. Other configurations require the purchase of a cable assembly.



The microphone assembly

Your headset may be shipped with the microphone assembly (boom microphone and cable) attached to the left earcup. If your headset is shipped with the microphone assembly packed separately, you can attach it to either earcup.

Attaching the microphone assembly

Choose the earcup (L or R) to receive the microphone assembly. Also, make sure that the earcup connector pins are clean and free of debris.

1.Use a Phillips screwdriver to loosen the two screws on the terminator cover near the bottom of the earcup where you want to attach the

microphone assembly.

2.Remove the terminator cover to reveal the connector pins on the earcup.

3.Carefully line up the microphone assembly to the small connector socket on the earcup.

4.Slide the connector into the socket until it reaches the stop.

L for left

Terminator Connector coverpins

Microphone assembly Connector pins

CAUTION: Do not force the connector into the socket, or earcup damage may occur.

5.Tighten the screws to secure the assembly.

6.Attach the terminator cover to the earcup that does not have the microphone assembly attached. Insert the screws, then align and tighten them.

Note: The headset will not work without the terminator cover installed.

CAUTION: Be sure to try the headset and fully test its operation before flight.



The battery compartment

The Bose® A20® Aviation Headset is shipped withfactory-setoperation defaults. If you want to alter these defaults, you can change the operation switches located inside the control module battery compartment. If you do not want to change any of the operation switches, skip ahead to “Inserting and replacing the batteries” on page 10.

Note: Foraircraft-poweredversions(5-pinXLR,6-pin,8-pin)batteries are not required for operation.

Opening the battery compartment

You must open the battery compartment to access the operation switches. Press down firmly on the battery compartment cover finger indent and slide the cover down. The cover is tethered to the module. Do not attempt to detach it.

Note: The battery compartment cover is designed to remain securely closed. You may need to use additional force when pressing down and releasing cover.

The operation switches

The operation switches control the Auto Off and Stereo/Mono functions.

Operation switches

To change the operation switches

1.Open the battery compartment.

2.If batteries are installed, remove them. In the battery compartment, you can observe and change the switch positions.



3.To change a switch position, use a pen or a small, flat-tippedscrewdriver to gently move the switch.

This table shows possible positions, default setting, and purpose for each switch.









Auto Off


Set at the factory to enable the Auto Off function. The headset



Default: ON

will turn off after 3 to 9 minutes of inactivity. To disable Auto



Off, set the switch to OFF. With the switch in OFF position, the




Acoustic Noise Cancelling® system will not turn off until you




press and hold the power button for at least one second.







Mono, Stereo

For most configurations, set at the factory for mono audio



Default: MONO

systems (to provide audio in both ears). Set it to stereo (ST)



if your aircraft has a stereo intercom.





Auto Off functionality

The Auto Off feature detects when the headset is not in use and shuts it off after several minutes to preserve battery power. The exact time it takes to shut off varies and can range between 3 to 9 minutes after you stop using the headset.

When the headset is running on battery power only and is not plugged in to an intercom, it will shut off even when there is an auxiliary input present.

If you are on a phone call and unplugged from an intercom, the headset will allow you to complete your call, then it will turn off approximately three seconds after the call is terminated.

Note: To use the headset when unplugged from the intercom to listen to auxiliary input audio or as aBluetooth® wirelesstechnology-enabledheadset to make or receive calls, we recommend you disable the Auto Off feature for uninterrupted functionality.

Inserting and replacing the batteries

CAUTION: If the batteries do not fit correctly, do not force them in. Forcing an improper connection will cause permanent damage to the control module.

To insert or replace the batteries

1.Turn off headset power.

2.Press down firmly on the battery compartment cover and slide the cover to release. The battery door is tethered. Do not detach the door from module.

3.Insert the two supplied alkaline AA batteries into the control module, observing proper polarity.

4.Replace the battery compartment cover.

Note: Replace batteries with alkaline batteries only. Do not use any other battery chemistries.



Connecting the headset to the aircraft

The Bose® A20® Aviation Headset can be configured to either plug into aircraft power or rely entirely on battery power.

Using the 6-pinplug

A single 6-pinplug inserted into the6-pinconnector provides the headset with aircraft power and intercom audio.

If your headset is aircraft-powered,a6-pinconnector must be installed and mounted to an aircraft panel. See “Mounting the aircraft panel connector” on page 31.

Note: An adapter is available from Bose to convert a6-pinconnector to a dual G/A or U174 plug for additional connection flexibility.

To connect the headset

1.Align the 6-pinplug to the connector keyway by matching the narrow bar on the plug to the slot on the connector.

2.Firmly press the plug into the connector jack.

Align keyway

Push plug in

To disconnect the headset

1.Pull back on the sleeve near the end of the 6-pinplug.

2.Gently continue pulling back to remove the plug from the connector.

CAUTION: Do not pull the connector out without first pulling back the sleeve. Forcing the connector out will damage the cable and/or the aircraft instrument panel.

Pull sleeve back, then pull plug out




Using the dual general aviation plugs

The most common battery powered (only) version of the headset has two general aviation (G/A) plugs that connect to the aircraft audio. Although the plugs look similar, the microphone plug is shorter, thinner, and has a slightly different shape than the intercom plug.

Insert the thicker intercom plug in first. It will only fit into one of the jacks. Then insert the thinner microphone plug into the other jack.



Using other plug types

The Bose® A20® Aviation Headset is also available with other types of plugs for connecting to various aircraft audio jacks. Thesesingle-plugconnectors should be inserted into the appropriate jack on your aircraft control panel. Refer to “Power and cable variations” on page 7.



Wearing and adjusting the headset

Proper fit on your head is important both for comfort and optimal noise reduction performance. Here are a few guidelines:

Use the left (L) and right (R) markings above the earcups to orient the headset properly.



As you put the headset on, lightly grasp each earcup and adjust it so its cushion is completely over your ear. You should feel an even, gentle pressure all around each ear.

Adjust the headband so it rests gently on top of your head.

Make your final adjustments with the headset powered on in a noisy environment.

In very loud conditions, such as during takeoff, you may experience a brief reduction in Acoustic Noise Cancelling® as the headset compensates for a momentary pressure change. If the problem continues when the sound level returns to normal, see “In case of difficulty” on page 27. If the problem persists, contact Bose® Technical Support for assistance.

Conditions related to fit

A low rumbling sound or frequent, brief losses of Acoustic Noise Cancelling noise reduction may indicate an improper fit or blocked earcup ports. See “Headset earcup openings” on page 23 for instructions on removing blockages.

During a long flight, you may feel a slight pressure point, which can be relieved by adjusting the headband position. Your experience with using the headset will help establish a sense of how it should sound and feel.

Microphone placement

Microphone placement is important for clear communications. With the headset on your head, make these adjustments:



1.Grasp the boom with your fingers and move the microphone up or down so it is level with your mouth.

2.Pull the microphone in toward your lips. Position the microphone with its talk side facing in. Though it will be slightly off center, the microphone should be 1/2 inch from the opening of your lips.

Mic label

Mic is too far away

Mic label is not facing

Mic is 1/2 inchmouth from mouth

3.Make sure the talk side of the microphone is facing your lips. Do not purse your lips.

Clothing clips

The control module cable is fitted with two clothing clips. Use the clips to attach the headset cable to your clothing, a safety harness, or an aircraft door pocket.

Press to open clip

Press to release and reposition clip along the cable



Using the control module

Use the control module to control the headset functions. There are two variations of the module; one featuring Bluetooth® wireless technology and one that has basic functions only.

Bluetooth control module

Conventional control module


Left/Right volume controls*



Power indicator



Power button










function button


Volume Up button






Audio Priority





Volume Down button


























*Control the intercom volume

Power button

Use the power button to turn Acoustic Noise Cancelling® on or off, and control indicator brightness.

Press the power button once to turn on Acoustic Noise Cancelling noise reduction.

Press and hold the power button for 1-2seconds to turn off Acoustic Noise Cancelling noise reduction.

Note: Repeated pressing of the power button will not hasten the power off event. If the unit does not power off, wait 3 seconds and press the power button again.



Double-clickthe power button to dim the power andBluetooth® wireless technology indicators. To toggle the indicators between dim and bright, rapidly press the power button twice.

Volume control

The left and right volume control wheels on the control module adjust the volume of the corresponding earcup. With Acoustic Noise Cancelling® off, volume control will be set to the maximum level.

CAUTION: Avoid setting the volume levels too high. Exposure to loud sounds may cause hearing damage.

Holding the control module upright and facing you:

Use the left wheel to adjust volume of the left earcup.

Use the right wheel to adjust volume of the right earcup.

Overall headset volume control requires adjustments at both the aircraft intercom or radio and at the headset control module. Even at its lowest setting, neither volume control wheel can completely turn off the volume.

Power indicator

New alkaline AA batteries will generally supply at least 45 hours of power for the headset. Battery life varies with the ambient noise level of the aircraft, temperature, ear cushion condition, use of the Bluetooth feature, and age of the batteries. The power indicator changes color to indicate the power status, as follows:

Indicator color

Power source

Type of light








Slow flashing

Power ON








Power ON and batteries good







Fast flashing

Power ON, but batteries low




(8 hours or less remaining)







Faster flashing

Power ON, but batteries very low*




(2 hours or less remaining)








Power OFF or batteries depleted





Note: Replace batteries with alkaline batteries only. Do not use any other battery chemistries.

*Bluetooth wireless technology is disabled to conserve the remaining power once the battery reaches this level.