BRUEL & KJAER 4914 User manual

. ...
..
InstructionManual
Rhino-Larynx Stroboscope Type 4914
A versatile and powerful fibre-optic strobo-
scope for examination and stroboscopic
motion analysis of the larynx and the upper
respiratory tract and sinuses. Gives a Olear
picture, in slow motion, of the movements
of the vocal cords under phonation, facilitat-
ing early diagnosis of malignant conditions
in the larynx. Because of its built-in auto-
matic tracking filter and informative LCD
symbol display, the Type 4914 is very easy
to use. All functions are controlled by
means of a pedal. The phase indication on
the display allows accurate determination
of
vocal cord movements.
Both standard
rigid endoscopes and flexible
fibrescopes can be connected directly for
examination purposes, or for colour video
recording of the stroboscopic motion. Con-
nection to an operation microscope facili-
tates fixed light or stroboscopic examina-
tion, and the
photographing of larynx de-
tails.
+ BrUel & Kjcer

RHINO-LARYNX STROBOSCOPE
TYPE 4914
From serial no. 1122475
April 1984

SAFETY REQUIREMENTS
This apparatus has been designed and tested according to Class II of IEC Publication
601-1 (Type BF), Safety of Medical Electrical Equipment, and has been supplied in safe
condition. The present Instruction Manual contains information and warnings which
should be
followed by the user to ensure safe operation and to retain the apparatus in
safe
condition. Special note should be made of the following:
SAFETY SYMBOLS AND WARNINGS
The apparatus is marked with a number of safety symbols and warnings. Whenever
these
symbols are encountered, it is important that the user refer to the relevant warn-
ing, caution and attention statements given in the Instruction Manual.
A
short explanation of the symbols marked on the apparatus is given below:
Symbol Name Description
A
Consult ACCOMPANYING DOCUMENTS when this sign
ATTENTION is
encountered on the apparatus , to avoid reducing
safety of the apparatus
WARNING! Avoid looking into the light path
[E BODY FLOATING:
isolated from earth. Maximum Pa-
Type
BF tient Leakage
Current
under: Normal Condition
~
100µA, Single Fault Condition ~ 500 µA
Hazardous voltage
Indicates high voltage storage capacitors which can
~
remain charged when the instrument is disconnected
from mains supply
I On
Power is "On" when the power switch is set to the upper
position. When set to "Off", the AC mains supply is
0
Off internally disconnected
/'-..../
Alternating Current
Indicates instruments should be powered from an AC
mains supply only
'<r
Potential Equalization
Safety connector for coupling to external equipment.
Conductor
Ensures that all equipment have the same chassis po-
tential
[g] Class
II Equipment
Double insulation
T00344GBO

GENERAL SAFETY PRECAUTIONS
Explosion Hazard
The
apparatus is not constructed for use in potentially explosive environments and
should
therefore not be operated in the presence of flammable liquids or anaesthetics.
Connection of Power
During installation
of the apparatus, check that it is set to match the available mains
voltage and that the correct fuses are installed.
The mains input socket, all
connectors and cables should be kept clean and dry at all
times.
Connection of other Apparatus
If a safe method
for connecting (coupling) instruments cannot be seen clearly from tech-
nical
data supplied, the user must consult the relevant manufacturers to ensure that the
safety
of the entire system of equipment is not impaired.
Equipment Failure
Whenever it is likely that the
correct function or operating safety of the apparatus has
been impaired,
it must be disconnected from the mains supply and secured against
unintended operation.
Service and Repair
Service and
repair of electro-medical equipment should only be carried out by the man-
ufacturer or by their authorised representatives, as otherwise all responsibility for the
operating safety, reliability and performance of the equipment is disclaimed.
Following
repair the safety of all apparatus should be checked by a qualified electronics
engineer or hospital safety personnel.
Electromagnetic Interference
Complies with FCC ClassB Device regulations and the (82)499/EEC rules.

CONTENTS
1. INTRODUCTION & SPECIFICATIONS {PRODUCT DATA) ................................................................................. 1
2. CONTROLS..................................................................................................................................................................3
2.1. FRONT PANEL .......................................................................................................................3
2.2. REAR PANEL..........................................................................................................................5
2.3. FOOT PEDAL .........................................................................................................................6
3. OPERATION................................................................................................................................................................. 7
3.1. PRELIMINARY ........................................................................................................................7
Environment and Handling ...................................................................................................7
Mounting .................................................................................................................................7
Connection
of Mains Supply................................................................................................8
Potential Equalization Conductor ........................................................................................8
Selection of display symbols for "FILTER READY" ..........................................................8
3.2. USE AND CARE OF LIGHT CABLE AE 6100.....................................................................9
3.3. MOUNTING THE CABLE LIFTER....................................................................................... 11
3.4. MOUNTING THE LARYNX MIRROR AND CONNECTING THE LIGHT-PROBE........... 11
3.5. CONNECTION OF THE FOOT PEDAL AND THE STETHOSCOPE COUPLER........... 12
3.6. GENERAL OPERATING MODE ..........................................................................................12
3.7. CLEANING AND DISINFECTION........................................................................................14
3.8. COOLING ..............................................................................................................................
15
4. USE WITH OTHER INSTRUMENTS ...................................................................................................................... 16
4.1. LARYNX MIRROR ................................................................................................................16
4.2. RIGID ENDOSCOPE ............................................................................................................16
4.3. FLEXIBLE FIBRESCOPE .....................................................................................................17
4.4. OPERATION MICROSCOPE...............................................................................................
17
4.5. CAMERA............................................................................................................................... 18
Motion during exposure time.............................................................................................19
Exposure time ......................................................................................................................
20
4.6. VIDEO CAMERA .................................................................................................................. 21
4.7. USE OF THE 4914 WITH OTHER ELECTRONIC INSTRUMENTS................................. 21
4.8. REFERENCES....................................................................................................................... 22
5. SERVICE AND REPAIR ........................................................................................................................................... 23

USES:
• Visual examination
of the larynx, upper respira-
tory tract and sinuses
• Stroboscopic observation
of the vocal cord mo-
tion in either slow motion or "frozen" in selected
positions
• Determination
of natural frequency of the voice
• Control
of vocal register function
• Diagnosis and control of treatment of voice disor-
ders and diseases of the vocal cords
• Objective determination of voice frequencies for
training singers, and evaluation
of vocal cord vi-
bration patterns
• Evaluation
of voice frequencies and vocal cord
motion during speech therapy
• Teaching and demonstrating to large audiences
by means
of closed circuit television and/or vid-
eo-recordings
FEATURES:
• Very simple operation with pedal control
of all
functions.
• Powerful stroboscopic and fixed light sources
provide excellent illumination
for direct observa-
BP0378-11
type 4914
Rhino-Larynx Stroboscope
tion as well as colour video recordings, even
through flexible fibrescopes
• Stroboscopic observation
of pathological voices
facilitated by the automatic tracking filter's ready
response -even to poor, noisy voices with short
phonation time. This is
an essential requirement
in everyday clinical life
• Combined light-probe and mirror-holder for stan-
dard larynx
mirrors
• Large self-explanatory symbol display providing
all relevant information
to guide examination
procedure
• Pedal controlled observation
of the laryngeal vi-
bratory phases
• Fast, powerful photo-flash synchronized by X-con-
tact on an ordinary camera
• Direct connection to standard rigid endoscopes
and flexible fibrescopes
• Possibility
of connection to operation
microscopes
• Complies with Safety Class II of IEC Publication
601-1 (Type BF)
• Very robust stethoscope-type larynx microphone
which is insensitive
to room noise
• Hygiene requirements easily met

The Rhino-Larynx Stroboscope
Type 4914 is a combination of strobo-
scope, fixed light source
and funda-
mental frequency counter in a single
unit.
These are optimized for exami-
nation of voice functions.
The instrument includes an auto-
matic level control and a tracking fil-
ter which detects and locks onto the
first harmonic frequency of the voice.
The voice signal is picked up by a
larynx microphone (stethoscope cou-
pler)
and transmitted acoustically to
the instrument where it is transduced
into an electrical signal. By means of
an automatic level control, a tracking
filter and a phase locked loop, a pulse
train is generated which closely repre-
sents
the first harmonic frequency
(the
fundamental frequency) of the
voice.
From this pulse train the voice fre-
quency is
counted and displayed. The
LIGHT SOURCE:
Combined Xenon and Halogen light source
LAMPS:
Halogen Lamp: 150 W.
Expected life 50 h.
Stroboscopic Lamp: Half peak intensity du-
ration : -5 µs; Energy : approx . 0,7 J per pulse
Expected life : 38 million single flashes equal
to 90 h at a max. frequency of approx.
118 Hz, or 1 thousand single photo flashes
with 50% reduction in light output
FREQUENCY RANGE:
Microphone Trigger: 60 -1500 Hz
External Generator: 60 - 2000 Hz
OPERATING MODES:
(Controlled by pedal)
Fixed Light: Using Halogen Lamp
Phase Delay (Stroboscopic Light): Variable
0° to 360°
Photo: Remote activation of single flash via
camera flash-contact. Reset time 30 s
Slow Motion (Stroboscopic Light): 1,4 Hz
(fixed frequency)
Type of Light
electronic circuits are intended for fre-
quency
measurement of sustained
vowels.
The phase of the input signal is con-
tinuously
compared with a reference
phase.
This reference phase is either
continuously changing (slow motion
operating mode) or it can be held at a
fixed value selected using
the pedal
(phase delay). Each time the input
signal phase is equal to the reference
phase, a synchronizing signal is gener-
ated for the stroboscope lamp and the
trigger output. The stroboscope lamp
flashes for approx. 5 µs and is then
dark until the next trigger signal. If
the trigger flash input is activated be-
fore
the synchronizing signal, a large
condenser passes
an additional charge
through the lamp. This extends the
short flash to give a total flash time of
approx. 80 µs, which is sufficient to
expose photographic film.
Specifications 4914
TRIGGERING:
Normal triggering by means of robust stetho-
scope-type larynx microphone and acoustic
coupler to instrument. Alternatively, via Trig-
ger Input
INPUT /OUTPUT:
All trigger inputs and outputs are floating
Trigger Input: BNC coaxial socket
Input Voltage: 1 - 10 V RMS
Trigger Output: BNC coaxial socket
Output Voltage : 10 V Peak. Approx. 14 µS
positive pulses
Flash-Trigger Input: BNC 3-pole socket for
connection of photo cable
Microphone Input: Acoustical from Stetho-
scope Coupler to built-in microphone
Light Output: Via selected output coupler for
the desired light receiving device
Pedal Connector: 6 pole DIN connector
ELECTROMAGNETIC COMPATIBILITY:
Complies with Class B computing device of
American FCC (Federal Communication
Commission) Rules
llluminance [k lux]
(at distance from end of optical cable)
25mm 50mm 100mm
Halogen light 240
80
20
Stroboscope light
1 60 20 5
Light Exposure [k luxs]
Photo flash2
24 8 2
1 Mean value at 100 Hz
T00273GBO
2 Each shot
B0µs (hall peak intensity duration)
These values are reduced
if optical cables other than the B&K standard cable are used. For exposure calculations consider reductions from
additional optical systems
A 150 W halogen lamp is built into
the same lamp assembly as the strobo-
scope lamp.
When it is activated a
solenoid moves a small
mirror into its
light
path to direct the light to the
light output.
The selected light output from the
instrument is transferred to the light-
probe
mirror-holder or other optical
devices via a flexible light cable with
superior light carrying capabilities.
The light output available from the
optic cable is given in the specifica-
tions below.
Both halogen lamp and stroboscope
lamp generate considerable heat and
it is recommended that they be used
intermittently to extend the life of the
lamps. However, if used for long peri-
ods a
thermostat activated fan keeps
the internal temperature within ac-
ceptable limits.
SAFETY:
Complies with IEC 601-1 Class II Type BF
ENVIRONMENT:
Temperature Range: + 5 to 40 °C (+ 41 to
104 ° F)
Humidity: 0 to 90% RH non-condensing (at
30 ° c)
POWER REQUIREMENTS:
100; 115; 127; 200; 220 or 240 V (50 to 60 Hz)
± 10% AC; 200 VA. Complies with Safety
Class II of IEC 601-1 (Type BF)
CABINET:
Supplied as model A (light-weight metal cabi-
net) or model C as A but for rack mounting
DIMENSIONS:
Metal cabinet , excluding knobs and feet
Height: 177 mm (7,0 in)
Width: 430 mm (16,9 in)
Depth: 320 mm (12,6 in)
WEIGHT: 18 kg (39,7 lbs)
ACCESSORIES INCLUDED:
1 Flexible Light Cable .......................... AE 6100
1 Light-Probe Mirror-Holder ............... AE 6200
1 Larynx Mirror No.5............................. QA 0113
1 Larynx Mirror No.7............................. QA 0114
1 Larynx Mirror No.9............................. QA 0115
1 Output Coupler (Storz)...................... UA 0845
1 Output Coupler (Olympus)............... DB 2632
1 Blank Output Coupler .. . .. .............. .. . .. DP 0594
1 Stethoscope Coupler ........... .. ........... UA 0776
1 Pedal......................... ........ ............ .. .... .. UA 0727
1 Cable Lifter ............................. .. .... ....... UA 0807
1 Accessory Tray ...................................GV 1895
1 Power Cable ........................................ AN 0020
1 Photo Trigger Cable ........ .. ...... .... . ... .. AO 0375
2 BNC Plugs......
.. ... ................. .. ............... JP 0035
1 6-pin DIN Plug......................................JP 0600
1 Set of Fuses
ACCESSORIES AVAILABLE:
Spare Xenon Light Tube .. .................. .. VS 1006

2.1. FRONT PANEL
POWER:
MICROPHONE:
PEDAL:
LIGHT:
2. CONTROLS
-I
Rllino-La,vn>< Stroboscope
Type 4 914
" '
---------
00
•
0
..... ,
....,...,_
• llrilel&K)IOr -•
Fig. 2. 1. Front panel of Rhino-Larynx Stroboscope Type 4914
Switch for mains power. When set to "I", the DISPLAY lights of the
Type 4914
show a head with speech indication, and a foot placed over
a pedal indicating that the instrument is ready for measurement. See
chapter 3.1.5. When set to "O" the instrument is switched off.
Input accepting the stethoscope coupler tube (included). This is used
to feed the acoustic signal to the Microphone inside the instrument
which triggers the Stroboscopic Lamp.
6-pin socket accepting the 6-pin screw-lock plug of the Pedal Cable.
24 mm diameter, 1 mm pitch threaded flange for light transmission to
which couplers are connected to provide correct placement of various
light receiving devices. The Coupler DB 2632 is intended for Cable
AE 6100 supplied, and for Olympus fibrescopes. See sections 3.2. and
4.3.
The
Coupler UA 0845 is designed for use with Wolf and Storz rigid
endoscopes and other devices which may be converted to the Storz
output configuration. For other devices a Blank Coupler DP 0594 is
provided.
& The supplied Couplers are electrically isolated to ensure the BODY
FLOATING
safety requirements, and the Light Cable AE 6100 is also
electrically isolated.
3

FLASH-TRIGGER
INPUT:
DISPLAY:
4
& WARNING! Avoid looking into the light path. Although no permanent
damage will occur, momentary blinding may be experienced. After pro-
longed exposure to the Stroboscope light, painful eye irritation is to be
expected.
3-pole coaxial socket accepting the Photo Trigger Cable AQ 0375 pro-
vided with the Type 4914. It is used to trigger single "Photo" flash
ignitions via the flash contact of a camera. Triggering may also be
carried out using a standard 2 pole BNC plug. When the Photo Trigger
Cable is connected, a camera appears on the front panel DISPLAY.
See Fig. 2.2.
The
display has the following elements:
Fig. 2.2. Elements
of the liquid-crystal-display
1. a head with
2. speech indication to show that the filter is ready to search for a
voice frequency, and suggesting that the patient produce a sound
3. a camera which indicates that a cable plug is connected to the
FLASH-TRIGGER INPUT
4. blinking arrows to indicate that the Photo-flash Condenser is
charged and ready to fire a flash
5. four-digit (each with 7 elements) display for frequency or phase
values
6. a degree symbol for phase measurements
7. the "Hz" indication for frequency measurements
8. a foot placed over a pedal to suggest using the pedal to obtain
measurements
9. a light bulb indicating that a powerful light-source is in use. If no
light actually appears at the light output the lamp, or its fuse, may
be broken.
10. "FILTER" and

2.2. REAR PANEL
FUSES:
MAINS VOLTAGE:
AC MAINS INPUT:
TRIGGER INPUT:
TRIGGER OUTPUT:
-
,l
V
-
11. "READY". These are normally switched off. They provide the same
information as 1. and 2. Either or all of 1., 2., 10. and 11. may be
used
to indicate that the filter is ready.
Behind the Display is
placed an electro-illuminescent panel which pro-
vides a pleasant green backlight. In bright environmental illumination
the
display appears as dark figures on a light grey background. When
room lightning is reduced -as is often the case in ENT clinics -the
green backlight dominates and provides a clear contrast to the dark
letters and figures.
Tu99oi<
'°*'"' Ch.tP\lt
-
@@
•
• -
Fig. 2.3. Rear panel of Rhino-Larynx Stroboscope Type 4914
2 Fuse holders,
accepting two 2,5 A, 250 V slow blow fuses (B & K No.
VF 0060)
for 100 to 127 V mains operation or two 1,25 A, 250 V slow
blow fuses (B & K No. VF 0027) for 200 to 240 V mains operation. To
check and fit the appropriate fuses, see section 3.1.3.
6-position switch for selection of the correct mains voltage setting as
described in section 3.1.3.
2-pin socket accepting the Power Cable AN 0020 provided for connec-
tion to a 100, 115, 127, 200, 220 or 240 V ± 10% (50 to 60 Hz) single
phase AC mains supply. Before connecting a supply, the mains voltage
setting and fuse checks given in section 3.1.3 should be carried out to
ensure safe operation of the instrument.
Equipotential Screw connected to a main equipotential bonding con-
ductor when required by relevant local standards.
2-pole coaxial socket accepting standard BNC plugs for triggering via
an
external source. Input voltage 1 -1 OV RMS, input impedance 1O kn.
(Transformer input).
2-pole coaxial socket accepting standard BNC plugs. Output signal
(floating) is 1O
V, 14 µs positive pulses, output impedance approx.
115 Q.
5

2.3. FOOT PEDAL
6
Fig. 2.4. Foot Pedal
The pedal contains a potentiometer which is turned by the pedal
movement, and
two microswitches which are controlled by cams on
the
potentiometer axle.
The
microswitches control the selection of four different operating
modes, three of which are found in distinct pedal positions: free, fully
down, and lifted
to a mechanical stop. The fourth mode is covered by
the range between free and the mechanical stop, and the
potentiome-
ter becomes significant in these pedal positions.

3. OPERATION
3.1._ PRELIMINARY
3.1.1. Environment and Handling
3.1.2. Mounting
The Rhino-Larynx Stroboscope Type 4914 has been designed for operation in environ-
ments with
ambient temperatures between +5 to +40 °C (+41 to 104 ° F) and humidities
up
to 90% RH (non-condensing). For safe operation, avoid use in environments contain-
ing volatile liquids and gasses. Also verify that the Type 4914 is set to match the avail-
able
supply voltage and that the correct fuses are installed before each use of the
instrument.
The Type 4914 may be used free standing on its
four plastic feet or, for easier viewing,
the
front may be raised by folding down the metal stand attached to the front feet.
Fig.
3. 1. The Rhino-Larynx Stroboscope Type 4914 with front raised
using the stand on the base of the instrument. The Accessory
Tray GV 1895 in front is fixed onto the table edge with dou-
ble-sided adhesive tape
The
Accessory Tray (GV 1895) included may be fixed onto a table edge by means of
double-sided adhesive tape (see Fig. 3.1.). Alternatively it may be fixed to a wall by
fastening
screws through the two holes in its back.
7

3.1.3. Connection of Mains Supply
Before connecting a mains supply, the following mains voltage setting and fuse checks
should be carried out to ensure safe operation of the instrument.
Mains Voltage Setting
The Type 4914
may be powered from 100, 115, 127, 200, 220 or 240 V ± 10% (50 to
60 Hz) single phase AC mains lines. To select the correct mains voltage setting, use a
small
coin or wide-blade screwdriver to turn the MAINS VOLTAGE Selector on the rear
panel until the appropriate voltage setting on the Selector lines up with the black arrow
printed on the panel.
Fuse Rating
The
two mains fuses are contained in Fuse Holders immediately above the MAINS
VOLTAGE
Selector on the rear panel and may be released using a screwdriver to turn
the
centre of the Holder. For operation from 100 to 127 V supplies the two fuses should
be 2,5 A
slow blow (B & K No. VF 0060), whilst for 200 to 240 V supplies they should be
two 1,25 A slow blow (B & K No. VF 0027). Make sure that only fuses of the required
rated
current and of the specified type are used for replacement. The use of mended
fuses
or the short circuiting of the fuse holder is prohibited.
Supply Connections
Once the
mains voltage setting and fuses have been checked, the mains supply may be
connected to the mains input of the Type 4914 using the supplied Power Cable AN 0020.
3.1.4. Potential Equalization Conductor
The
Equipotential Screw should be connected to a mains equipotential bonding conduc-
tor when this is required by hospital rules etc. The Connector is identified by a symbol
as shown in Fig. 3.2.
831950
Fig. 3.2. The symbol for the Equi-
potential Screw on the
rear of the Type 4914
Any potential equalization conductor connected to the Equipotential Screw should be
identified throughout its length by green and yellow coloured insulation.
3.1.5. Selection of display symbols for "FILTER READY"
8
It is possible to choose different displays to indicate that the Filter is ready. When the
instrument is delivered it is set so that the display shown in Fig. 3.3. indicates that the
Filter is ready. The alternative displays are shown in Figs. 3.4. and 3.5., and
instructions
for changing these displays can be found in the Service Manual.

Voice Frequency, Hz Trigger Phase,0
Fig. 3.3. The "FILTER READY" display of Type 4914 as delivered from
the factory
Voice Frequency, Hz
Trigger Phase,
0
Fig. 3.4. Alternative setting of the display
Voice Frequency, Hz
Trigger Phase ..
0
Fig. 3.5. Display using a combination of the settings used in Figs. 3.3.
and 3.4.
3.2. USE AND CARE OF LIGHT CABLE AE 6100
The
Coupler DB 2632 is supplied for fitting the Type 4914 with its 1,8 m long, Flexible
Light Cable AE 6100 (see Fig. 3.6.). The Coupler screws into the LIGHT flange on the
front panel of the Type 4914 and is equipped with a centre hole for push-fit fastening the
tapered metal sheath at the input end of the Cable. Besides facilitating easy attachment
of the Cable, the Coupler ensures that the input face of the Cable is accurately aligned
with the light output of the Type 4914.
9

Fig. 3.6. Connection of the Light Cable AE 6100 using the coupler
DB 2632
.For operation at a flash frequency of 100 Hz (mean value), the average illuminance ob-
tained is as indicated in Table 3.1.
llluminance [klux]
Type of Light (at
distance from end of optical cable)
25mm
50mm 100mm
Halogen light 240 80 20
Stroboscope light
1 60 20 5
Light Exposure [kluxs]
Photo flash2 24 8 2
1 Mean value
at 100Hz T00361GBO
2 Each
shot 80µs (half peak intensity duration)
These values are reduced if optical cables other than the B&K standard cable are used. For exposure
calculations consider reductions from additional optical systems
Table 3.1. Average illuminance provided by Type 4914 plus Light Ca-
ble AE 6100 at the flash frequency of 100 Hz (mean value)
For use with other types of optic cable a Blank Coupler DP 0594 is supplied. The dimen-
sions of this Coupler are shown in Fig. 3.7., and when drilled with an appropriate sized
centre hole it can accommodate cables up to 17,5 mm in diameter. For optimal light
output it is important that the input face of the optic cable protrudes just under 40 mm
from the flange of the Coupler. See Fig. 3.7.
& The end of the light cable must not protrude more than 40 mm from the flange of the
Coupler. The
diameter of the optic cable at its far end must not exceed 8 mm.

Input face of light cable
I
--lllf--- - -~ ~ - ----
'
Max. 0 8mm
(23) 6
Max. 40
9
2 12
Centre hole
to be bored
to accept
light cable
with diameter
up to 17, 5mm
fU0602
Fig. 3. 7. Dimensions (in mm) of the Blank Coupler DP 0594 for correct
fitting and alignment of light cables
To prevent damage to light cables, avoid bending or twisting them sharply. Also take
care not to scrape their input or output faces against metal objects. Always unplug the
light cable from the Type 4914 by gripping them by their handle. To clean the cables,
lightly rub the input and
output faces with the end of a soft cloth which has been
moistened in alcohol or water containing a few drops of mild soap solution. On no
account use other strong cleaning agents. Further details concerning cleaning and disin-
fection are given in section 3.7.
3.3. MOUNTING THE CABLE LIFTER
Two threaded holes are located towards the front of both the left and right hand side
panels of the Type 4914 for mounting the Cable Lifter. To mount the Cable Lifter, first
remove the black plastic cap covering the lower screw supplied with it. The Cable Lifter
should then be screwed to the side panel of the Type 4914. If the lower screw is over-
tightened, the arm of the Cable Lifter cannot be moved between the three guide posi-
tions. Once the Cable Lifter is mounted, the black plastic cap should be fitted over the
lower screw again.
3.4. MOUNTING THE LARYNX MIRROR AND CONNECTING THE LIGHT-PROBE
To mount one of the supplied Larynx Mirrors, the mirror shaft is fitted into the black,
spring-loaded locking ring on the Light-Probe Mirror -Holder. Press the locking ring in,
insert the larynx mirror shaft, and then release the locking ring. The mirror face may be
positioned against the end of the Light-Probe to provide extra support. It can then be
rotated to obtain the optimum light path direction for viewing.
To
connect the Light-Probe to the Type 4914, the female socket of the light cable should
be pushed
onto the Light-Probe plug input so that the socket clicks into the groove on
the plug. The
Light-Probe can be disconnected by removing the socket from the light
probe plug.
11

Fig. 3.8. The Light-probe Mirror-holder and three larynx mirrors
3.5. CONNECTION OF THE FOOT PEDAL AND THE STETHOSCOPE COUPLER
The Pedal is connected by inserting the screw-lock 6-pin DIN-plug of the pedal cable
into the PEDAL Socket on the front panel of the Type 4914. The screw-lock is then
tightened to hold the DIN-plug in position.
The Stethoscope Coupler is connected by pushing the free end of the rubber tube firmly
over the black MICROPHONE Connector on the front panel of the Type 4914.
3.6. GENERAL OPERATING MODE
12
Carry out the preliminary checks and adjustments necessary (see section 3.1 ), connect
the Light Cable, Light-Probe, Stethoscope Coupler and Pedal (see sections 3.2 to 3.5).
1. Set the "POWER" switch to "I" (On) and the Display will show that the instrument is
ready for measurement. See Fig. 3.9.
Voice Frequency, Hz Trigger Phase,0
Fig. 3.9.
2. Hold the Stethoscope Coupler lightly against the patients neck in the vicinity of the
larynx. It is often preferrable that the patient himself holds the Coupler during the
consultation since this may be more comfortable for him.
Any sound produced in the larynx is then picked up by the Stethoscope Coupler and
fed to the Microphone Input.

3. An examination can be started with a test of the voice frequencies and register
functions of the patient. This is carried out without touching the Pedal by letting the
patient utter the desired sustained vowels while the measured frequencies are dis-
olaved (see Fia. 3.10.).
Voice FrequencyI Hz Trigger Phase,0
Fig. 3.10.
Although the automatic tracking filter and other circuitry are not intended for measure-
ment of the speaking voice, some users do get useful information by letting the patient
speak freely, while observing the rapidly changing frequency read-out of the Display.
4. A normal examination sequence may be carried out as described in the following.
(a) A Larynx Mirror is fitted into the Light-probe Mirror-holder.
(b) The Mirror may then be heated in the normal way over an alcohol flame without
special consideration for the light probe.
Note: Heating over the flame for more than a few seconds at a time may, however,
cause the polished end
of the light probe to be less light transmitting. If the light trans-
mission is felt to be reduced the two ends should be cleaned with an alcohol wetted
cloth. In case where the polished finish is degraded a repolishing could be carried out.
(c) The Mirror is placed in position for viewing the larynx while the pedal is pressed
to its lowest position thereby switching the fixed Halogen Light on for orienta-
tion. Using this light the vocal cords and other parts of the larynx may be
examined. The instrument display is shown in Fig. 3.11.
Voice Frequency, Hz Trigger Phase,0
Fig. 3.11.
13

(d) The patient is prompted to pronounce a sustained vowel and at the same time
the foot is eased upwards to the mechanical stop of the pedal. A stroboscopic
light is, thereby, produced to show the motion of the vocal cords at a slow
motion frequency of approx. 1,4Hz with an apparent motion sequence equal to
that of the real motion which appears at the voice frequency. A study of the
details in the motion is thereby possible. The Display shows the
voice frequen-
cy. See Fig. 3.12.
Voice Frequency, Hz Trigger Phase,0
Fig. 3.12.
5. For some investigations it is of interest to know the relative duration of different
parts of the glottal function. For this purpose the pedal may be released beyond its
stop into the variable phase region. In this region, a sustained vowel from the pa-
tient produces a "frozen" stroboscopic picture of the vocal cords. The picture may
be chosen at any part of the motion sequence and the relative phase of each setting
may be read-off from the Display in 10° steps. See Fig. 3.13.
Voice Frequency, Hz Trigger Phase,
0
Fig. 3.13.
6. By totally releasing the Pedal, the Stroboscope Lamp will stop operation and the
instrument will return to the "FILTER READY" position. It is now possible to start a
new examination sequence (see point 3. or point 4.).
3.7. CLEANING AND DISINFECTION
14
1. The instrument itself, the Cable Lifter and the Pedal may be cleaned by wiping them
with a tightly wrung cloth using a solution of mild detergent. Care should be taken
not to wet the cables, plugs and sockets.