Northern Airborne Technology 247 User Manual

Installation and Operation Manual

Model 247

Audio Mixing Amplifier

(size the image to allow for optimal viewing).

SM247

ISSUE 2.00

Northern Airborne Technology Ltd.

1925 Kirschner Road

Kelowna, BC, Canada.

V1Y 4N7

Telephone [phone]

Facsimile [phone]

Issued on the authority of Northern Airborne Technology Ltd.

Copyright 2005

Model 247 Audio Mixing Amplifier

SM247 Installation and Operation Manual

Table of Contents

Section Title Page

1. Description

1.1 Introduction 1-1

1.2 Product Description 1-1

1.3 Design Features 1-1

1.4 Specifications 1-1

1.4.1 Electrical Specifications 1-1

1.4.2 Physical Specifications 1-2

1.4.3 Environmental Specifications 1-2

1.4.4 Product Approval 1-2

2. Installation

2.1 Introduction 2-1

2.2 Unpacking and Inspection 2-1

2.2.1 Warranty 2-1

2.3 Continued Airworthiness 2-1

2.4 Installation Procedures 2-1

2.4.1 Warnings 2-2

2.4.2 Cautions 2-2

2.4.3 Cabling and Wiring 2-2

2.4.4 Mechanical Installation 2-3

2.4.5 Electrical Installation 2-3

2.4.6 Pin Assignment 2-3

2.4.7 Post Installation Checks 2-4

2.5 Adjustments 2-4

2.6 Accessories Required But Not Supplied 2-5

2.7 Installation Drawings 2-5

3. Operation

3.1 Introduction 3-1

3.2 General Information 3-1

Installation and Operation Manual Page iii

ENG-FORM: 820-0114.DOT

CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIR BORNE TECHNOLOGY LTD.

Model 247 Audio Mixing Amplifier

SM247 Installation and Operation Manual

Section 1 Description

1.1 Introduction

Information in this section consists of product description, design features and specifications for the
Model 247 Audio Mixing Amplifier. The Model 247-001 is also included in this manual – any other
derivative product information shall be contained in the applicable manual supplement, which may be
obtained from Northern Airborne Technology Ltd. as required.

Review all notes, warnings and cautions.

1.2 Product Description

The Model 247 Audio Mixing Amplifier contains three electrically independent audio mixing circuits with
four input channels and one output channel each.

The Model 247 is designed for use as a multipurpose mixing amplifier for mixing Aural Warnin g, Cockpit
Voice Recorder or virtually any aircraft audio signals. Each input is adjustable to accept 0.25 Vrms
microphone input signals, headphone audio signals from a standard aircraft audio system, o r re ceiver
input signals up to 50 mW. Mic bias for each input channel is user selectable. Access for gain
adjustment and mic bias selection is made by cover removal.

Outputs from the Model 247 are designed to drive any impedance from 8 ohms up to 10K ohms. Output
power is limited by 100 ohm resistors on each output. If additional inputs are needed beyond the four
inputs provided for each mixing circuit, an output from one mixer circuit can be fed to the input of another
mixer thereby increasing the size of the mixer. The Model 247 can also drive headsets for headset
amplifier applications.

The Model 247 gain is established at a maximum of 12 dB with the bias/ground jumpers installed.
However, for input signals which do not require DC BIAS or a 600 ohm input impedance, the bias/ ground
jumper for a given input can be removed which will result in an additional 6 dB gain increase (doubling of
the gain).

1.3 Design Features

The Model 247 standard configuration is designed for driving non-DC biased (ground refe renced) loads.
The Model 247-001 includes bi-polar output capacitors for compatibility with DC biased loads such as DC

biased microphone inputs to other equipment.

1.4 Specifications

1.4.1 Electrical Specifications

Power Supply: 28 VDC at 150 mA maximum (each circuit).

Input impedance: 600 Ω (15KΩ with gnd/bias jumper removed)

Maximum current (3 mixer circuits combined) = 450 mA

Section 1 Rev: 1.00 Issue 2 Page 1-1

ENG-FORM: 800-0115.DOT

CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIR BORNE TECHNOLOGY LTD.

Model 247 Audio Mixing Amplifier

SM247 Installation and Operation Manual

Output impedance: 100 Ω
Frequency Response: Flat within +3dB from 300 to 6,000 Hz
Distortion: <1% THD+N from 300 to 6,000 Hz
Gain Range: >12 dB
Output: 4.5 Vrms (33mW) into 600 Ω, Outputs are current limited

Mic bias 18 Vdc at 30 mA (600 Ω source impedance) individually sele ctable

1.4.2 Physical Specifications

Height 41.40 mm (1.63 in) maximum
Depth 76.96 mm (3.03 in) maximum
Width 76.96 mm (3.03 in) maximum excluding flanges

102.36 mm (4.03 in) maximum incl uding flanges
Weight 0.6 kg (0.42 lbs)
Enclosure Conversion coated aluminum
Mounting Bulkhead Mount: four # 8 screws

Note: Model 247-001 includes bi-polar output capacitors for
compatibility with DC biased loads such as microphone inputs

1.4.3 Environmental Specifications

Temperature -55° to +70° C
Altitude -15,000 to 70,000 feet
Qualification of the Model 247 Audio Mixing Amplifier was completed in accordance with

RTCA/DO-160C Env. Cat. [A2F2]-BA(CL)XXXXXXZ(BZ)AAATZ(XXC2)XX

Note: Refer to Environmental Qualification Form located in Section 2 of this Manual for complete details

of the environmental categories.

1.4.4 Product Approval

FAA: TSO-C50c (RTCA/DO-214 Class

Ib, RTCA/DO-160C).

Section 1 ends

Section 1 Rev: 1.00 Issue 2 Page 1-2

ENG-FORM: 800-0115.DOT

CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIR BORNE TECHNOLOGY LTD.