Sony MDR-RF940RK Leaflet

Operating Instructions

Manual de instrucciones

Sony Corporation © 1996   Printed in Japan

3-858-839-12(1)

Insert two R6 (size AA) batteries by
matching the + and – on the batteries
to the + and – in the battery
compartment.

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Close the battery compartment lid.

When to replace the batteries
Replace both batteries with new ones
when the POWER indicator dims, and a
hissing noise increases.

Notes on batteries
To avoid damage to the system caused
by battery leakage and corrosion;
– Install the batteries with the correct

polarity.

– Do not try to recharge the batteries.
– Remove the batteries if the system is

not to be used for a long period of
time.

In case of battery leakage, wipe off any
deposit in the battery compartments
before installing new batteries.

( Operating the system

Select the radio frequency with the
CHANNEL selector switch.
Select the same channel on the
headphones and the transmitter.

Turn on the audio/video equipment
then the transmitter.

Put on the headphones and the
power turns on automatically.

Adjust the volume.

If the transmitter is connected to the headphones
jack of the source equipment, set the volume of
that equipment as high as possible without
distorting the audio signal.

Auto power on/off function
When you remove the headphones, the
power turns off automatically.  Do not
apply pressure to the left ear pad when
not using the headphones, otherwise the
headphones will be switched on.

/

Mute function
If a hissing noise is heard when the
headphones are used outside of the
effective range (see the next section), the
mute function will be activated and the
sound will not be heard from the
headphones.  To restore the sound,
move near toward the transmitter.

After listening to a program
Take the headphones off before turning
off the transmitter.  If you turn off the
transmitter first, you may hear some
noise.

The optimum distance is up to
approximately 130 feet (40m) without
the system picking up some interference.
However, the distance may vary
according to the surroundings and
environment. If the system picks up
some noise while using it within the
above mentioned distance, reduce the
distance between the transmitter unit
and the headphones, or select the other
channel.

Notes
•When you use the headphones inside the

effective areas of the transmitter, the transmitter
can be placed in any direction from the listener.

•Even within the signal reception area, there are

some spots (dead point) where the RF signal can
not be received.  This characteristics is inherent to
RF signals, and does not indicate malfunction.
By slightly moving the transmitter, location of
the dead point can be changed.

No sound/
Muffled sound

Distortion

Loud
background
noise

Turn on the transmitter
first, then put on the
headphones.

Check the connection of the
audio/video equipment or
the AC power adaptor.

Check that the audio/video
equipment is turned on.

Turn up the volume on the
connected audio/video
equipment, if the
transmitter is connected to
the headphones jack.

The mute function is
activated.
Use the headphones near
the transmitter.

Replace both batteries of the
headphones.

Replace the batteries in the
transmitter if the
transmitter is used by
battery operation.

If the transmitter is
connected␣ to␣ the␣ headphones
jack, turn down the volume
of the connected audio/
video equipment.

Replace both batteries of the
headphones.

Replace the batteries in the
transmitter if the
transmitter is used by
battery operation.

Move closer to the
transmitter.  As you move
away from the transmitter,
more noise is likely to be
heard.

If the transmitter is
connected to the
headphones jack, turn up
the volume of the connected
audio/video equipment.

If noise is heard when the
transmitter is hooked to the
TV headphones jack, try
connecting from LINE OUT.

Replace both batteries of the
headphones.

Replace the batteries in the
transmitter if the
transmitter is used by
battery operation.

When the ear pads become dirty or
damaged, you can get replacements
from your Sony dealer.  Replace them as
illustrated below.

Remove the old ear pad by pulling it
out of the groove on the housing.

Place the new ear pad on the
housing and insert the edge of the
pad into the groove as illustrated.

Make sure that the entire edge of the ear
pad is securely inserted into the groove.

( Additional information

• When the headphones are not to be

used for a long period of time, remove
the batteries to avoid damage caused
by battery leakage and subsequent
corrosion.

• When the transmitter is not to be used

for a long period of time, disconnect
the AC power adaptor from the AC
outlet holding the plug.  Do not pull
on the cord.
Also remove the batteries to avoid
damage caused by battery leakage and
subsequent corrosion.

• Do not leave the wireless stereo

headphone system in a location subject
to direct sunlight, heat or moisture.

Notes on headphones
Preventing hearing damage
Avoid using headphones at high
volume.  Hearing experts advise against
continuous, loud and extended play.  If
you experience a ringing in your ears,
reduce the volume or discontinue use.

Caring for others
Keep the volume at a moderate level.
This will allow you to hear outside
sounds and to be considerate to the
people around you.

If you have any questions or problems
concerning the system that are not
covered in this manual, please consult
the nearest Sony dealer.

Be sure to bring the headphones and the
transmitter to the Sony dealer when
requiring repair work.

Connect the transmitter to a power
source.

Notes
•When the AC power adaptor is connected to the

transmitter, internal batteries are automatically
disconnected.

•Use only the supplied AC power adaptor.  Do

not use any other AC power adaptor.

•When you connect the connecting cord directly

to an earphone jack, the audio signal will not be
output through the right channel.  In such a case,
use the separately sold PC-236HG plug adaptor.

To obtain power from batteries
The transmitter can also be operated by
use of four R6 (size AA) batteries.

Open the battery compartment lid
on the bottom of the transmitter.

Insert four R6 (size AA) batteries by
matching the + and – on the batteries
to the + and – in the battery
compartment.

Close the battery compartment.

When to replace the batteries
Replace all the batteries  with new ones
when the POWER indicator dims, and a
hissing noise increases.

Open the battery compartment lid
on the left inner side of the head
band.

Sony alkaline battery
LR6 (SG)

Sony battery R6P (SR)

40

20

Sony alkaline battery
LR6 (SG)

Sony battery R6P (SR)

40

20

( Getting started

Check that you have the following
items:

• The transmitter

• AC power adaptor

• Connecting cord (phono plugs ˜

stereo mini jack)

• The headphones

Connect the transmitter to audio/
video equipment.

a To connect to a headphones jack

b To connect to LINE OUT or REC OUT

jacks

Carrier frequency

913.5 – 914.5 MHz

Channel

Ch1, Ch2

Modulation

FM stereo

Frequency response

18 – 22,000 Hz

RF Power

Less than 94 dBµV/m at 3 m

Power source

DC 4.5 V: supplied AC power
adaptor
DC 6 V: 4 x R6 (size AA) battery

Audio input

stereo mini plug

Dimensions

Approx. 90 mm dia x 35 mm
(3 

5

/

8

 x 1 

7

/

16

 in.) (w/h)

Mass

Approx. 200 g (7.1 oz.)
incl.batteries

Power source

DC 3 V: 2 x R6 (size AA) battery

Mass

Approx. 270 g (9.5 oz.) incl.
batteries

Plug adaptor PC-236HG
    (stereo mini jack ˜ monaural mini plug)

Design and specifications are subject to change
without notice.

thoroughly and retain it for future
reference.
Some features are:
• Wireless system that allows you to

listen to a program free from the
restriction of a cord within 130 feet
from the transmitter.

• High fidelity sound reproduction
• Compact transmitter which operates

on battery power and AC power
supplied through the supplied AC
power adaptor

• Comfortable Circum-aural

headphones

• Automatic ON/OFF function on

headphones to preserve battery power

• Mute function to avoid noise when no

audio signal is available.

The system for this equipment utilizes very
high frequency signals in the 900 MHz band
so the receiving performance may deteriorate
due to the surroundings.  The following
examples illustrate conditions that may
reduce the possible receiving range or cause
interference with reception.
• Inside a building with walls containing

steel beams.

• Area with many steel file cabinets, etc.
• Area with many electrical appliances

capable of generating electromagnetic
noise.

• Transmitter is placed on a metal

instrument.

• Area facing roadways.
• Noise or interfering signals exist in the

surroundings due to radio transceivers in
trucks, etc.

• Noise or interfering signals exist in the

surroundings due to wireless
communication systems installed along
roadways.

WARNING
You are cautioned that any changes or
modifications not expressly approved in
this manual could void your authority to
operate this equipment.

The model number is located inside the
battery compartment of the transmitter
and the right inner side of the head
band.
The serial number is located inside the
battery compartment of the transmitter
and inside of the battery compartment of
the headphones.
Record these numbers in the spaces
provided below. Refer to them
whenever you call upon your Sony
dealer regarding this product.

Model No. MDR-RF940RK
 Transmitter TMR-RF940R
 Headphones MDR-RF940R
Serial No.
␣ Transmitter 
 Headphones 

Thank you for purchasing the Sony
MDR-RF940RK Wireless Stereo
Headphone System.  Before operating
the unit, please read this manual