User manual GARMIN GMA 240 AUDIO PANEL INSTALLATION MANUAL REV. A, JUN, 2008

[. . . ] GMA 240 Installation Manual GMA 240 MUS IC SQ OFF/ VOL C OM1 C OM1 MIC C OM2 C OM2 MIC MUTE MON NAV1 P ILOT IS O NAV2 IC S AUX1 AUX2 SQ 1 2 1-2 TE L MUTE MUS IC P ILO T R ADIO 1 TEL VOL MUSIC VOL PULL C OP ILO T 190-00917-01 June, 2008 Revision A © Copyright 2008 Garmin Ltd. or its subsidiaries All Rights Reserved Except as expressly provided herein, no part of this manual may be reproduced, copied, transmitted, disseminated, downloaded or stored in any storage medium, for any purpose without the express prior written consent of Garmin. Garmin hereby grants permission to download a single copy of this manual and of any revision to this manual onto a hard drive or other electronic storage medium to be viewed and to print one copy of this manual or of any revision hereto, provided that such electronic or printed copy of this manual or revision must contain the complete text of this copyright notice and provided further that any unauthorized commercial distribution of this manual or any revision hereto is strictly prohibited. 151st Street Olathe, KS 66062 USA Telephone: 913. 397. 8200 Aviation Panel-Mount Technical Support Line (Toll Free) 1. 888. 606. 5482 www. garmin. com Garmin (Europe) Ltd. [. . . ] When the PILOT ISO key is selected, the pilot and copilot will hear each other but will be isolated from the passengers. When the CREW ISO configuration is selected, the copilot's headphone jack must be wired in parallel with the pilot headset output. PILOT ISO MUSIC: This input configures music to be heard by the pilot during PILOT ISO mode (or by the pilot and copilot if crew isolate mode is configured). Normally, the isolated ICS positions do not hear music. Page 2-4 Rev. A GMA 240 Installation Manual 190-00917-01 BUTTON PRESS TONE ENABLE: This input enables an audible tone to be heard when a button press is detected. MUTE ON COM TX: This input configures the audio panel to mute all selected radios (COM, NAV, AUX) except the mic selected COM (COM selected for transmission) when a PTT key is activated for COM transmit. 2. 4 Noise Because the audio panel is a point in the aircraft where signals from many pieces of equipment are brought together, care must be taken to minimize effects from coupled interference and ground loops. Coupled interference can sneak into audio system interconnecting cables when they are routed near large AC electric fields, AC voltage sources, and pulse equipment (strobes, spark plugs, magnetos, EL displays, CRTs, etc). Interference can also couple into audio system interconnecting cables by magnetic induction when they are routed near large AC current-carrying conductors or switched DC equipment (heaters, solenoids, fans, autopilot servos, etc). Ground loops are created when there is more than one path in which return currents can flow, or when signal returns share the same path as large currents from other equipment. These large currents create differences in ground potential between the various equipment operating in the aircraft. These differences in potential can produce an additive effect at an audio panel signal input. The audio panel may "see" the desired input signal plus an unwanted component injected by ground differentials, a common cause of alternator-related noise. This is the main reason why all audio jacks should be isolated from ground. Terminating audio shields just at one end eliminates another potential ground loop injection point. Single-point grounding cannot be overstressed for the various avionics producing and processing audio signals. Single-point, in this context, means that the various pieces of equipment share a single common ground connection back to the airframe. Good aircraft electrical/charging system ground bonding is also important. The wiring diagrams and accompanying notes in this manual should be followed closely to minimize noise effects. GMA 240 Installation Manual 190-00917-01 Page 2-5 Rev. A 2. 5 GMA 240 Mounting The GMA 240 mounting surface must be capable of providing structural support and electrical bond to the aircraft to minimize radiated EMI and provide protection from High-Intensity Radiation Fields (HIRF). See Section 3. 4 for installation instructions. NOTE Rear support is recommended to ensure a sturdy mount. Figure 2-2. A GMA 240 Installation Manual 190-00917-01 3 3. 1 INSTALLATION PROCEDURE Unpacking Unit Carefully unpack the equipment and make a visual inspection of the unit for evidence of damage incurred during shipment. To justify a claim, save the original shipping container and all packing materials. [. . . ] Pin 16 Connector Pin Name P2401 MASQ INHIBIT* IN Description Ground to disable Master Avionics Squelch circuitry. This will cause alerts and selected radios to be heard at all times without needing to exceed the mute threshold. This causes an increase in background noise from the inputs during quiet output. In this configuration, the copilot headset jack should be wired in parallel with the pilot headset output. [. . . ]