An audio indicator is required for TSO-C126 approval. The indicator, i.e. “buzzer” (Artex P/N 452-6505) is powered by the ELT and, therefore independent of the aircraft power system. When the ELT is activated, the buzzer ‘beeps’ periodically. The time between pulses lengthens after a predetermined transmitter ‘on’ time.
The buzzer may be located anywhere on the aircraft; however, it is recommended that it be placed near the ELT unit so it can be heard outside the aircraft when the engine(s) is (are) off. It is assumed that with a running engine the cockpit light will warn the pilot. Mounting the buzzer in the cockpit is not recommended due to the distracting sound it produces when the ELT is activated. This buzzer operates in tandem with the ELT panel indicator and serves as a redundant indicator.
NOTE: Although the wording of RTCA/DO-204 indicates installation in the cockpit, Artex recommends that the buzzer be placed aft or near the ELT unit. Artex holds an FAA deviation approval (FAA Reference #96-103S-522, dated September 10, 1996).
The buzzer can be mounted in two ways: either using the mounting ‘ears’ at its base or in a panel mount configuration using the plastic bezel nut. The mounting position of the buzzer should be such that the buzzer opening is not prone to collecting liquid or other material, as this buzzer is not sealed and not waterproof. Suggested mounting is with the buzzer orifice pointing down. The rear of the buzzer can be sealed with RTV; however, the front must be left open. Ground the black lead and connect the red lead to the ELT buzzer output (pin 8 of the D-sub).
2.7 Cable harness and Wiring
. Artex recommends 22 or 24 AWG wires or shielded 4-wire cable for long cable runs where electrical noise (EMI) interference is a concern. Larger diameter wire may be used. All Artex testing and qualification was performed using 22 and 24 AWG wire. Use a high quality wire such as MIL-W-16878, M22759, M27500 or their commercial equivalent.
. A ‘drip loop’ should be constructed in the harness near the ELT to divert moisture from the connector. This is extra cable length used to form a U-shaped bend just before the connector. Water or other fluids will flow down to the bottom of the loop and drip off, diverted away from the connector. Adjust length of harness to allow for the loop before installing connector.
Grounding:
. Some installations use the airframe as a ground connection between the ELT and the remote switch. The ground resistance from the remote switch, through the airframe to the ELT ground connection should be less than 10 ..
. Typically, the shield of the 4-wire cable is used as the ground wire (see Figures 10 and 13), allowing use of a four wire shielded cable.
. A ground may be connected at either the ‘panel end’ or the ‘ELT end’ of the harness, but both locations should not be grounded. This prevents current flow thorough the shield from other equipment (ground loop). A convenient harness ground connection is pin 9 of the remote switch connector. This is connected internally to pin 6 (ground) and is provided for this purpose (see Figures 10 through 13). 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：DESCRIPTION, OPERATION, INSTALLATION AND MAINTENANCE MANUAL ME406P ELT(17)
