Model 240 Passenger Speaker Amplifier
SM240 Installation and Operation Manual
Section 1 Rev: 1.00
Issue 4
Page 1-1
ENG-FORM: 800-0114.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.
Section 1 Description
1.1
Introduction
Information in this section consists of product description, design features and specifications for the
Model 240 Passenger Speaker Amplifier. All derivative product information shall be contained in the
applicable manual supplement, which may be obtained from NAT as required.
Review all notes, warnings and cautions.
1.2
Product Description
The Model 240 Passenger Speaker Amplifier mixes audio from various sources for output to cabin
speakers. It is a remotely controlled, electronic unit, which operates upon command from switches and
potentiometers in the cockpit or cabin of the aircraft.
1.3
Design Features
The Model 240 provides left/right audio taken from an external stereo receiver/music source, to the cabin
speakers.
The Model 240 provides Fasten Seat Belt and No Smoking sign chime tones, a Cabin Call ringer tone,
ADF, Pilot Select Com (PSC), TV, Briefer and Cabin Paging audio, to the cabin speakers.
All inputs and operating modes are electronically switched. Ground signals, supplied by manual switches
in the cockpit, enable the electronic switches in the Model 240. The circuitry is arranged to provide Paging
and Briefer audio priority; the PA MIC or Briefer switch signals essentially open the Stereo Left, Stereo
Right, ADF 1, ADF 2, PSC and TV audio inputs. Microphone bias current is available from the Model 240
for the PA MIC microphone input.
A musical chime tone is provided to the cabin speakers to alert the passengers of a change in the Fasten
Seat Belt or No Smoking sign status. A Cabin Call ringer tone is also provided to the cabin speakers for
the cockpit to cabin intercom system.
1.4
Specifications
1.4.1 Electrical
Specifications
Input specifications are expressed in volts RMS (Vrms), rather than milliwatts, to avoid any misunderstanding.
Input Signals:
ADF:
Two single, switched audio inputs for ADF, etc. Input level is 7.75 Vrms.
PSC:
One single, switched audio input compatible with the Pilot Select
Com (PSC) output of dB Systems Model 418, which provides a
1.00 Vrms signal, produced from a summation of selected COM,
DME and MKR receivers.
TV:
One single, switched audio input for TV etc. Input level is 1.00 Vrms.
