Garmin GMA 340 Manual

GMA 340

AUDIO PANEL

Pilot’s

Guide

Front Panel Controls

1. Marker Beacon Lamps

2. Marker Beacon Receiver Audio Select/Mute Button

3. Marker Beacon Receiver Sensitivity Indicator LED.

4. Marker Beacon Receiver Sensitivity Selection Button

5. Unit On/Off, Pilot Intercom System (ICS) Volume

6. Pilot ICS Voice Activated (VOX) Intercom Squelch Level

7. Copilot and Passenger ICS Volume Control (Pull out for Passenger

Volume)

8. Copilot/Passenger VOX Intercom Squelch Level

9. Crew Isolation Intercom Mode Button

10. Pilot Isolation Intercom Mode Button

11. Passenger Address (PA) Function Button

12. Speaker Function Button

13. Transceiver Audio Selector Buttons (COM1, COM2, COM3)

14. Transmitter (Audio/Mic) Selection Buttons

15. Split COM Button

16. Aircraft Radio Audio Selection Buttons (NAV1, NAV2, DME, ADF)

17. Annunciator Test Button

18. Locking Screw Access

19. Photocell - Automatic Annunciator Dimming

MKR

BCN

ICS

COM/

NAV

On, Off, and Fail-Safe Operation

The GMA 340 is powered off when the left small knob (5) is rotated fully CCW into the detent.

To turn the unit on, rotate the knob clockwise past the click. The knob then functions as the pilot

ICS volume control. A fail-safe circuit connects the pilot’s headset and microphone directly to

COM1 in case power is interrupted or the unit is turned off.

Lighting

LED button annunciator and marker beacon lamp intensity are controlled automatically by a

built-in photocell on the front panel. Nomenclature backlighting is controlled by the aircraft dim-

mer buss.

Transceivers

Audio level is controlled by the selected COM radio volume controls.

Selection of either COM1, COM2, or COM3 for both MIC and audio source is accomplished by

pressing either COM1 MIC, COM2 MIC, or COM3 MIC (14). The active COM audio is always

heard on the headphones.

Additionally, each audio source can be selected independently by pressing COM1, COM2, or

COM3 (13). When selected this way, they remain active as audio sources regardless of which trans-

ceiver has been selected for microphone use.

When a microphone is keyed, the active transceiver’s MIC button LED blinks approximately

once per second to indicate that the radio is transmitting.

Split COM

Pressing the COM 1/2 button (15) activates the split COM function. When this mode is active,

COM1 is dedicated solely to the pilot for MIC/audio while COM2 is dedicated to the copilot for

MIC/audio. The pilot and copilot can simultaneously transmit in this mode over separate radios.

Both pilots can still listen to COM3, NAV1, NAV2, DME, ADF, and MKR as selected. The split COM

mode is cancelled by pressing the COM 1/2 button a second time.

When in the split COM mode the copilot may make PA announcements while the pilot contin-

ues using COM1 independently. When the PA button is pressed after the split com mode is acti-

vated, the copilot’s mic is output over the cabin speaker when keyed. A second press of the PA but-

ton returns the copilot to normal split COM operation.

NOTE

If the COM radios utilize a “transmit interlock” system, the split COM function

may require that this feature is enabled. Refer to the radio installation manual

for guidance. GARMIN makes no expressed or implied guarantees regarding

the suitability of the split COM feature in a given installation.

COM Swap Function

The GMA 340 allows the use of a remote mounted switch (typically on the yoke) to alternately

transfer the active microphone back and forth between COM1 and COM2. Pressing the remote

switch will have no effect if COM3 is the active transceiver. Ask your

installing agency

for details.

Aircraft Radios & Navigation

Audio level is controlled by the selected NAV radio volume control.

Pressing NAV1, NAV2, DME, ADF (16), or MKR (2) (see MKR Beacon Receiver) selects each

audio source. A second button press deselects the audio. In addition, the GMA 340 provides inputs

for an unswitched aircraft radio (TEL RINGER) and an un-muted, unswitched aircraft radio (ALT

WRN).

Speaker Output

Pressing the SPKR button (12) selects the aircraft radios over the cabin speaker. The speak-

er output is muted when a COM microphone is keyed. The GMA 340 speaker output level can

be adjusted by your installing agency.

PA Function

The PA mode is activated by pressing the PA button (11). Then, when either the pilot’s or

copilot’s microphone is keyed, the corresponding mic audio is heard over the cabin speaker. If the

SPKR button is also active, then any selected speaker audio is muted while the microphone is keyed.

The SPKR button does not have to be previously active in order to use the PA function. Pilot and

copilot PA microphone speaker levels are adjustable

by your installing agency

NOTE

Auxiliary Entertainment Inputs

The GMA 340 provides two stereo entertainment inputs: MUSIC1 and MUSIC2. MUSIC1 is

soft-muted during all aircraft radio activity and normally during ICS activity. MUSIC2 is a non-

muted input. These inputs are compatible with popular portable entertainment devices such as cas-

sette tape or CD players. The headphone outputs of these devices are used and plugged into

MUSIC1 or MUSIC2. Two 3.5 mm stereo phone jacks should be installed in a convenient location

for this purpose. MUSIC1 and MUSIC2 have characteristics that are affected by the active intercom

mode. Refer to the table on page 5.

Intercom System (ICS)

Intercom volume and squelch (VOX) are adjusted using the following front panel knobs:

• LEFT SMALL KNOB—Unit ON/OFF power control and Pilot ICS volume. Full CCW detent

position is OFF.

• LEFT LARGE KNOB—Pilot ICS mic VOX squelch level. CW rotation increases the amount

of mic audio (VOX level) required to break squelch. Full CCW is the “HOT MIC” position

(no squelch).

• RIGHT SMALL KNOB—IN position: Copilot ICS volume. OUT position: Passenger ICS

volume.

• RIGHT LARGE KNOB—Copilot and passenger mic VOX squelch level. CW rotation

increases the amount of mic audio (VOX level) required to break squelch. Full CCW is the

“HOT MIC” position.

Each of the six microphone inputs have dedicated VOX circuits to ensure that only the active

microphone(s) is/are heard when squelch is broken. This represents a vast improvement over the

party-line systems and reduces the amount of background noise in the headphones during cockpit

communications. After the operator has stopped talking, the intercom channel remains momentar-

ily open to avoid closure between words or normal pauses.

The GMA 340 provides three intercom modes: PILOT, CREW and ALL. Mode selection is

accomplished using the PILOT and/or CREW buttons. Pressing a mode button activates the corre-

sponding ICS mode. Pressing again deactivates the mode. The ALL mode is active when neither

PILOT nor CREW LEDs are lit. To switch from PILOT to CREW mode, press the CREW button;

from CREW to PILOT, press the PILOT button. An LED ON indicates the isolation mode is active.

• PILOT mode isolates the pilot from everyone else and dedicates the aircraft radios

to the pilot exclusively. The copilot and passengers share communication between

themselves but cannot communicate with the pilot or hear the aircraft radios.

• CREW mode places the pilot and copilot on a common ICS communication chan-

nel with the aircraft radios. The passengers are on their own intercom channel and

can communicate with each other, but cannot communicate with the crew or hear

the aircraft radios.

• ALL mode allows full intercom communication between everyone plugged in to

the GMA 340. Aircraft radios are also heard by all.

• MUSIC1 and MUSIC2 stereo entertainment inputs are affected by the intercom

mode selected.

The following table summarizes the ICS operation for the different modes supported by the

GMA 340.

MUSIC1 is normally muted during ICS activity. However an installation option is available to

disable ICS MUTE. Then muting of MUSIC1 will not occur due to ICS activity. A panel mounted

switch may be installed for this function. The MUSIC1 mute trip level is adjustable by the installa-

tion agency.

MODE

PILOT

(LED

LIT)

CREW

(LED

LIT)

ALL

(LEDs

OFF)

PILOT HEARS

Selected Radios.

Pilot.

Selected Radios.

Pilot. Copilot.

MUSIC1.

Selected Radios.

Pilot.

Copilot.

Passengers.

MUSIC1.

COPILOT HEARS

Copilot.

Passengers.

MUSIC1.

Selected Radios.

Copilot. Pilot.

MUSIC1.

Selected Radios.

Pilot.

Copilot.

Passengers.

MUSIC1.

PASSENGER HEARS

Passengers.

Copilot.

MUSIC1.

Passengers.

MUSIC2.

Selected Radios.

Pilot.

Copilot.

Passengers.

MUSIC1.

MUSIC1 MUTING

TRIGGERED BY

Copilot or passenger

intercom activity.

Aircraft radio activity.

MKR activity.

Pilot or copilot activity.

Aircraft radio activity.

MKR activity.

Intercom activity.

Marker Beacon Receiver

The marker beacon is used as part of an ILS approach and in certain instances, to

identify an airway. In addition to the normal marker beacon functions, the GMA 340

provides an audio muting function. The lamps illuminate, and an associated keyed-

tone is heard (when MKR audio is selected), when the aircraft passes over a 75 MHz

marker beacon transmitter.

The lamp and audio keying for ILS approach operation are summarized below.

The marker beacon audio level is aligned at the factory to produce its rated audio output.

However, the audio output level is adjustable by your

installing agency

The GMA 340’s marker beacon receiver controls are located on the left side of the front panel

(1-4). The SENS button selects either high or low sensitivity as indicated by the HI or LO LED being

lit. Low sensitivity is used on ILS approaches while high sensitivity allows operation over airway

markers or to get an earlier indication of nearing the outer marker during an approach.

The marker audio is initially selected by pressing the MKR/mute button (2). If no marker bea-

con signal is received, then a second button press will deselect the marker audio. This operation is

similar to selecting any other audio source on the GMA 340. However, if the second button press

occurs while a marker beacon signal is received, then the marker audio is muted but not deselect-

ed. The button’s LED will remain lit to indicate that the source is still selected. When the current

marker signal is no longer received, the audio is automatically un-muted. While in the muted state,

pressing the MKR/mute button deselects the marker audio. The button’s LED will extinguish to indi-

cate that the marker audio is no longer selected.

The marker beacon lamps operate independently of any audio selection and cannot be turned

off. The GMA 340 can drive external marker lamps if required.

Audio

Frequency

400

1300

3000

Audio Keying Lamp Actuated

Blue (Outer)

Amber (Middle)

White (Airway/Inner)

www.garmin.com

GARMIN International, Inc.

1200 E. 151st Street, Olathe, KS USA 66062-3426

Telephone (913) 397-8200 or 1-800-800-1020 FAX (913) 397-8282

GARMIN (Europe) Ltd.

Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51 9AQ U.K.

Telephone 011-44-1794-519944 FAX 011-44-1794-519222

GARMIN (Asia) Corp.

3F, No.1, Lane 45, Pao Hsing Road, Hsin Tien, Taipei, Taiwan, ROC

Telephone 886-02-2917-3773 FAX 886-02-2917-1758

Part Number 190-00149-00 Rev. C

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