EQUIPMENT MANUAL 700-16-1
700/700-16-1
CONFIDENTIAL AND PROPRIETARY TO COBHAM
Page 1
EQUPMENT MANUAL
MODEL 700-[ ]
1.0 OPERATING INSTRUCTIONS AND EQUIPMENT LIMITATIONS
This document makes references to dB Systems, Inc. and NAT Seattle, Inc. Please note that
dB Systems, Inc. and NAT Seattle, Inc. have been changed to Cobham. For all references to
dB Systems, Inc. or NAT Seattle, Inc. herein, substitute Cobham.
The conditions and tests required for TSO approval of this article are minimum performance
standards. It is the responsibility of those installing this article either on or within a specific type
or class of aircraft to determine that the aircraft installation conditions are within the TSO
standards. TSO articles must have separate approval for installation in an aircraft. The article
may be installed only if performed under 14 CFR part 43 or the applicable airworthiness
requirements.
The Model 700 Digital Audio Control Amplifier is a remotely controlled electronic unit that operates
upon digital signal command sent to it by the digital multiplexing unit or switch panel at its
respective audio control station. An example of such a switch panel would be Model 803. The
digital multiplexing unit or switch panel continuously reads the status of all audio control switches
and settings of potentiometers and compiles this information into the form of a digital signal. The
digital signal is sent to the Model 700 from the digital multiplexing unit or switch panel in RS-422
serial format via a twisted, shielded wire pair. The Model 700 receives and demultiplexes this
digital signal and converts it into useful audio control information.
The Model 700 is capable of switching and controlling the individual volume of up to 15 receiver
inputs. It also switches six sidetone inputs and an interphone line. In addition, four unswitched
and unmuted inputs are provided to accommodate an aural warning input and three auxiliary
inputs. Headphone and selected speaker outputs are isolated and a cockpit voice recorder (CVR)
output is a summation of the headphone and Hot microphone audio. The Hot microphone to CVR
audio channel is unswitched and unmuted, thus allowing Hot microphone audio to be recorded on
the cockpit voice recorder at all times. A pilot select COMM output is a summation of all selected
receiver inputs, excluding aural warning, auxiliary, sidetone, or interphone audio.
Receiver, sidetone, headphone, interphone and speaker audio, and all operating modes are
electronically switched and controlled by the digital signal information sent from the digital
multiplexing unit or switch panel. An electronic volume control attenuator is employed in each of
the 15 receiver audio input channels. Every receiver input attenuator has 25 dB of range and is
digitally controlled. Separate electronic volume control attenuators are provided for headphone
audio (35 dB range), speaker audio (35 dB range), sidetone audio (25 dB range), and interphone
audio (25 dB range). These volume control attenuators are also digitally controlled. Refer to the
applicable multiplexing unit or switch panel equipment manual for specific information on control
hardware required. Aural warning, auxiliary, CVR, and pilot select COMM audio channels do not
employ any individual electronic volume control attenuators; however, the volume of some CVR
audio is directly affected by the headphone volume control.
A voice activated switch (VAS or VOX) is incorporated in series with the Hot microphone input to
interphone channel. This feature allows Hot interphone operation without coupling of ambient
cockpit noise into the amplifier during times when the pilot is not talking. If the internal VAS pot
jumper is installed at the mating connector (see Figure 2, Wiring Diagram), then the threshold of
voice activation may be adjusted by an internal screwdriver adjustment through a hole in the cover