Northern Airborne Technology 251 User Manual

Installation and Operation Manual

Model 251

Passenger Speaker Amplifier

SM251

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 1998

Model 251 Passenger Speaker Amplifier

SM251 Installation and Operation Manual

Prepared By: Checked By: Certification: Approved By:

The status of this installation and operation manual is controlled by issue shown on the title page. The
status of each section is controlled by revision shown in the footer of each page. All revisions affecting
sections of this manual have been incorporated into the latest issue.

ISSUE/REVISION RECORD

Manual Issue

Number

Section

Revision Number

Revision Description Issue Date

2.00 Section 1 Rev: 1.00
Section 2 Rev: 1.00
Section 3 Rev: 1.00

Rewritten in full NAT format Oct 28, 2009

Installation and Operation Manual Page ii

ENG-FORM: 820-0114.DOT

CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIR BORNE TECHNOLOGY LTD.

Model 251 Passenger Speaker Amplifier

SM251 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 1-2

1.4.1 Electrical Specifications 1-2

1.4.2 Physical Specifications 1-4

1.4.3 Environmental Specifications 1-4

1.4.4 Product Approval 1-4

1.5 Unit Nomenclature 1-4

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 Operating Modes 2-4

2.4.7 Wiring Diagram 2-5

2.4.8 Pin Assignment 2-8

2.4.9 Post-Installation Checks 2-9

2.5 Adjustments and Connections 2-10

2.6 Accessories Required But Not Supplied 2-10

2.7 Installation Drawings 2-11

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 251 Passenger Speaker Amplifier

SM251 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 251 Passenger Speaker Amplifier. All 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 251 Passenger Speaker Amplifier is a remotely controlled, electronic unit that operates upon
command from remote switches and potentiometers in the cockpit or cabin of the aircraft.

1.3 Design Features

The Model 251 provides Seat Belt and No Smoking sign chime tones, a Cabin Call ringer tone, ADF, Pilot
Select Comm. (PSC), Briefer, and Cabin Paging audio (all in mono) to the cabin speakers. It also
provides audio from an external AM/FM stereo receiver/cassette tape or CD player (in stereo) to the cabin
speakers and auxiliary monitor outputs.

The left and right speaker amplifier channels are each powered through separate internal fuses so that a
failure in one speaker channel will not disable the other speaker channel or the remaining control circuitry.
The left and right monitor outputs are powered from a third power supply circuit.

A musical chime tone is provided to the cabin speakers to alert the passengers of a change in the Faste n
Seat Belt or No Smoking sign status. A Cabin Call ringer tone is also provided to the cabin for a cockpit
to cabin intercom system. The chime and ringer tones do not pass through either of the electronic
attenuators.

Each left and right speaker amplifier output rating is 28 Watts into 2 ohms (30 Watts typical) or 49 Watts
into 1 ohm. Both speaker amplifier outputs are internally protected against open and short circuits as well
as over-temperature (>105°C).

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 251 Passenger Speaker Amplifier

SM251 Installation and Operation Manual

1.4 Specifications

1.4.1 Electrical Specifications

Power Supply: 28 Vdc, 5 ampere maximum.

INPUTS

Section 1 Rev: 1.00 Issue 2 Page 1-2

ENG-FORM: 800-0115.DOT

:
ADF: Two individual, switched audio inputs for ADF1 and ADF2.

Input level is 7.75 Vrms.
PSC: One switched audio input compatible with the Pilot Select COMM

output of dB Systems cockpit audio control amplifiers (such as
Models 438 and 700), which provides a 1.00 Vrms signal
produced from a summation of selected COMM, DME and MKR
receivers. The PSC input can also be used for TV audio or other
similar audio.

TV: One switched audio input for TV (or other device). Input level is

1.00 Vrms.

Stereo Left: One switched differential audio input for the left audio channel

from an AM/FM Stereo receiver/tape or CD deck (or other
device). Input level is maximum 0.45 Vrms. (at maximum source
volume) and audio LO is not common to that of other inputs.

Stereo Right: Same as stereo left, switched by the same control input as

stereo left.

Brief: One switched audio input for automated cabin briefer audio.

Input level is 1.00 Vrms.

PA MIC: The microphone input used for cabin paging audio supplies bias

current and is compatible with carbon and amplified dynamic
microphones. Input level is 0.25 Vrms.

Paging Volume: Controls level of PA MIC and brief audio inputs to the PA

sidetone and left and right speaker outputs. Volume control
range is 30 dB (minimum) controlled by a 10,000-ohm, 1/2-Watt,
linear pot. Maximum volume is with maximum resistance.

Receiver Volume: Controls level of ADF, PSC and TV audio inputs to the left and

right speaker outputs. Volume control range is 30 dB (minimum)
controlled by a 10,000-ohm, 1/2-Watt, linear pot. Maximum
volume is with maximum resistance.

CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIR BORNE TECHNOLOGY LTD.

OUTPUTS

Right Speaker: The right speaker amplifier is designed for speech and music

Rated Power Load
49 W 1 ohm (40 Watts typical)
28 W 2 ohms (30 Watts typical)
15 W 4 ohms (18 Watts typical)

Left Speaker: Same as right speaker specification
Right Monitor: Delivers up to 26 milliwatts into 600 ohms continuously. Factory

Left Monitor: Same as right monitor specification
PA Sidetone: 6.7 milliwatts (2 Vrms) into 600 ohms continuous.

Rated and continuous power ratings are the same.
Chime Tone: Generated and supplied to left and right speaker and monitor

A 790 Hz tone followed by a 610 Hz tone (2-tone, HI/LO) is

Ringer Tone: Generated and supplied to left and right speaker and monitor

Frequency Response: Upper and lower frequency limits are adjustable. Stereo, ADF,

Harmonic Distortion (Thd+N): Less than 0.30 percent distortion, for stereo and less than 1% for

Isolation Between Channels: 60 dB, minimum.
Output Noise: Greater than 75 dB below rated, all outputs.

Model 251 Passenger Speaker Amplifier

SM251 Installation and Operation Manual

:

signals.
Rated power specification is the maximum power the amplifier

can continuously deliver into the maximum rated load without
clipping.

calibration is 1.6 mW (1 Vrms).

outputs when 12 to 32 Vdc is applied to or removed from
connector pins P50-31 or P50-32.

factory set for 3.5 VPP (at speaker outputs), adjustable from 1.0
to 6.9 VP-P and is also available at monitor outputs.

outputs when a ground signal is applied to connector pin P50-33.
Ringer tone is 700 ±75 Hz tone, ON for 1.8 ±0.1 second, then OFF
for 3.2 ±0.1second, repeat ing. Fact ory set for 1.5 VP -P (700 Hz
component) (at speaker outputs), adjustable from 0 to 5.2 VPP.

TV, and PSC inputs to speaker and monitor outputs are flat
within 3 dB from 40 Hz to 20,000 Hz. All other inputs to speaker,
monitor, or PA sidetone outputs flat within 3 dB from 300 Hz to
6,000 Hz.

ADF, TV and PSC to all outputs (40 Hz to 20 KHz). Less than
3% for PA and briefer to all outputs (300 Hz to 6 KHz).

Section 1 Rev: 1.00 Issue 2 Page 1-3

ENG-FORM: 800-0115.DOT

CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIR BORNE TECHNOLOGY LTD.

Model 251 Passenger Speaker Amplifier

SM251 Installation and Operation Manual

1.4.2 Physical Specifications

Height 2.470"
Depth 4.9000" max
Width 7.800" max. including flanges and excluding mating connectors
Weight 2.6 lbs
Mounting Bulkhead Mount (four (4) #8 screws)

1.4.3 Environmental Specifications

Temperature: -55 to +70°C (Operating) Thermal fold-back of the speaker

Operating Altitude: 70,000 feet max
Humidity 95% Non-condensing
Shock 15g (any axis)
Vibration RTCA/ DO-160C category CL
Qualification of the Model 251 Passenger Speaker Amplifier was completed in accordance with

RTCA/DO-160C Environmental Categories [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.

outputs occurs if the heatsink temperature reaches 105°C.

-55 to +85°C (Survival)

1.4.4 Product Approval

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

Ib, RTCA/DO-160C)

1.5 Unit Nomenclature

Examples of derivative products are given below. For full information contact Customer Service & Repair.
Model 251-001 Low pass filters adjusted for -3 dB attenuation at 90 Hz on left and right

speaker outputs.

High pass filters adjusted for -3 dB attenuation at 20 Khz on left and right

speaker outputs.

Designed for use with 4-inch speakers.

Section 1 Rev: 1.00 Issue 2 Page 1-4

ENG-FORM: 800-0115.DOT

CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIR BORNE TECHNOLOGY LTD.