ENC
ELECTRONIC
NOISE CANCELLING
HEADSETS
OWNERS MANUAL
2
SATISFACTION GUARANTEE
The idea of a guarantee that a product will function in accordance with certain
claims, and will be replaced or repaired if it fails to perform to those standards, has
been popular for decades. In these times, most guarantees promise safeguards
against failure over varying periods, and are worded such that proving fault with
the manufacturer has become primarily the customer’s responsibility.
A guarantee made by the David Clark Company assumes full responsibility for the
quality and the performance of the product, to your satisfaction; it is supported
by a policy of service to customers which is based on the premise that our
relationship is one of mutual honesty, requiring that we respond in a prompt,
positive manner to anyone who contacts us.
David Clark Company communication equipment has evolved to a performance level
of excellence that is appreciated by quality conscious people throughout the world.
We strive constantly for excellence in design, and performance, and have a
positive attitude toward constructive criticism, especially from our customers.
We have earned a reputation for excellence; we intend to keep it, and to
continue deserving your confidence!
Robert A. Vincent, President
CONTENTS
Description & Technical Information ............................................................. 3-4
Operation & Instructions ...............................................................................5-7
Features - H-10 Series .................................................................................... 8
Features - H10-66XL Series ............................................................................ 9
Features - H10-76XL and H10-76XP............................................................10
Accessories - Power Options ................................................................... 11-12
Maintenance & Cleaning ................................................................................13
Customer Service ............................................................................................BC
ELECTRONIC NOISE
CANCELLATION
DESCRIPTION & TECHNICAL INFORMATION:
How it works.
David Clark’s Electronic Noise Cancellation (ENC) headsets feature the latest
advances in electronic noise cancellation technology. They’re specially designed
for pilots of aircraft which generate noise at lower frequencies. Headsets relying
on passive noise control methods alone cannot suppress low frequencies as
effectively as mid and high range frequencies.
Opposites protect.
Unlike passive headsets, David Clark’s electronic noise cancellation headsets use
an electronically produced signal to cancel the offending noise. Low frequency
noise is sensed and an opposing signal of the same sound level is generated.
The result is cancellation of the noise before it reaches your ears.
Hear what’s important.
With low frequency noise canceled, you’ll hear essential communications clearly,
and with less strain. Sounds within the range of the human voice, such as air
traffic messages and conversations with other pilots, will be easier to verify.
Such improved audio comfort leads to alert, and safer flying.
cancelling
effect
3
4
Passive versions of these headsets already exhibit excellent noise reduction ratings
(NRR). Test measurements indicate an increase in attenuation at lower frequencies
when ENC is switched on. At the present time there is no ANSI test standard for
independent measuring of the effectiveness of Electronic Noise Cancellation.
Fail-safe:
An important product feature is true “fail-safe” operation. By having dual earphone
drivers, which are electronically independent, no interruption of communication can
result from failure of the ENC system or its power source.
Headset:
Sensitivity: 90dB +- 5dB SPL on flat plate coupler, re 1mW input @ 1 KHz.
Frequency Response: 350-3,000 Hz +- 6dB re 1 KHz.
Impedance: Monaural, 150 Ω nominal; Stereo, 300 Ω nominal
per side. (Does not apply to H10-76XL series.)
Microphones:
M-7A:
■ Incremental DC and Dynamic AC, 50 Ω ± 20%.
■ Sensitivity: 400 mV ± 6dB into 150 Ω AC load @ 1 KHz for 114dB SPL input.
M-101:
■ Low Impedance Position: 5 Ω nominal, sensitivity .07-.14 mV@ 103 dB SPL
into 5 Ω load @ 1000 Hz.
■ High Impedance Position: 400 mV ± 6 dB @114 dB SPL 1/4”, 1000 Hz bias
8-16 volts behind 470 Ω and with a 150 Ω AC input impedance.
M-87:
■ Microphone designed to be used in aircraft requiring a LOW IMPEDANCE
microphone. Microphone impedance is nominally 5 Ω.
■ Sensitivity: .05 to 11 mV across 5 Ω load at 1000 Hz with an input of
103 dB SPL.
■ Frequency response: 200-6000 Hz
ATTENUATION
5
OPERATION
Electronic noise cancellation is an “electrical” process. Power to drive the circuitry
is obtained from either the Portable Battery Power Module (models ending in “XL”
or “X”) or the aircraft’s electrical system (models ending with “XP”).
XL-9V
Instructions
Introduction
The model XL-9V battery pack uses a
9 volt alkaline battery to provide power
to the headset ENC system. The XL-9V
features an Auto Shut Off function to save
the battery if the power switch is left on
when the headset is not in use. The Auto
Shut Off feature operates by sensing loss
of microphone DC bias voltage when the
headset is unplugged or aircraft audio
system is shut off.
A switch is provided inside the battery
compartment (see Fig.1) to control the
Auto Shut Off feature.
The XL-9V is
shipped from the factory with the switch in the DISABLE position,
which will provide continuous power to the ENC system whenever
the power switch is on.
GENERAL AVIATION PORTABLE BATTERY MODULE
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