Intelect MOBILE STIM User Manual Model 2777 2005

TABLE OF CONTENTS

Intelect® Mobile Stim

FOREWORD... 1 PRODUCT DESCRIPTION... 1 SAFETY PRECAUTIONS... 2 PRECAUTIONARY DEFINITIONS... 2 CAUTIONS... 3 WARNINGS... 5 DANGERS... 7 INDICATIONS, CONTRAINDICATIONS, AND ADVERSE EFFECTS... 9 Indications for VMS, Russian, TENS, High Voltage Pulsed Current (HVPC), Interferential, and Premodulated Waveforms... 9 Additional Indications for Microcurrent, Interferential, Premodulated, VMS™, and TENS Waveforms... 9 Indications for Galvanic Continuous Mode... 9 Contraindications... 9 Additional Precautions... 9 Adverse Effects... 10 OVERVIEW... 11 Common Terms... 11 NOMENCLATURE... 15 SPECIFICATIONS... 19 UNIT SPECIFICATIONS... 19 WAVEFORM SPECIFICATIONS... 20

SETUP... 27 MOUNTING THE UNIT ON THE WALL... 27 INSTALLING THE BATTERY PACK... 31 CHARGING THE BATTERY PACK... 33 USING THE BATTERY PACK... 33 ELECTROTHERAPY PATIENT PREPARATION... 34 Electrode Placement... 34 DURA-STICK® Electrodes... 35 Reusable Carbon Electrodes... 35 DURA-STICK® Electrode Instructions... 36 Connecting Lead Wires... 36 Securing Electrodes... 36 Reusable Carbon Electrodes... 37 Connecting Lead Wires... 37 Conductive Medium... 37 Securing Electrodes... 37 OPERATION... 38 STARTING, STOPPING, AND INTERRUPTING THERAPY... 38 CREATING A USER PROTOCOL... 45 USING PROTOCOLS... 50 SYSTEM UTILITIES... 53 Audible Tones... 53 Changing Protocol Parameters... 53 Changing Default Protocols... 55 Brightening or Dimming the LCD... 59 i

TABLE OF CONTENTS

Intelect® Mobile Stim

Restoring Factory Protocols... 59 Changing Languages... 61 Restoring Factory Settings... 64 Viewing Unit Version Information... 66 TROUBLESHOOTING... 69 ERROR CODES... 69 ACCESSORIES... 71 Standard Accessories... 71 Optional Accessories... 71 Mains Power Cords... 71 MAINTENANCE... 72 MAINTAINING THE UNIT... 72 Cleaning the Unit... 72 FACTORY SERVICE... 72 WARRANTY... 73

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FOREWORD

Intelect® Mobile Stim

This manual has been written for the users of the Intelect Mobile Stim units. It contains general information on the operation, precautionary practices, and maintenance information. In order to maximize use, efficiency, and the life of the unit, read this manual thoroughly and become familiar with the controls, as well as the accessories before operating the system. Specifications put forth in this manual were in effect at the time of publication. However, owing to Chattanooga Group's policy of continual improvement, changes to these specifications may be made at any time without obligation on the part of Chattanooga Group. Before administering any treatment to a patient, the users of this equipment should read, understand, and follow the information contained in this manual for each mode of treatment available, as well as the indications, contraindications, warnings, and precautions. Consult other resources for additional information regarding the application of electrotherapy.

Product Description The Intelect Mobile Stim, designed and manufactured by Chattanooga Group, offers a new dimension in clinical electrotherapy made possible by software design and digital signal processing. Effectiveness of this treatment is dependent upon correct use. If treatment times are exceeded, the therapy may not result in positive clinical outcomes. Stay current with the latest clinical developments in the field of electrotherapy. Observe all applicable precautionary measures for treatment. Keep informed of appropriate indications and contraindications for the use of electrotherapy. This equipment is to be used only under the prescription and supervision of a licensed practitioner.

©2005 Encore Medical Corporation or its affiliates, Austin, Texas, USA. Any use of editorial, pictorial, or layout composition of this publication without express written consent from Chattanooga Group of Encore Medical, L.P. is strictly prohibited. This publication was written, illustrated, and prepared for distribution by Chattanooga Group of Encore Medical, L.P.

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SAFETY PRECAUTIONS

Intelect® Mobile Stim

PRECAUTIONARY DEFINITIONS The precautionary instructions found in this section and throughout this manual are indicated by specific symbols. Understand these symbols and their definitions before operating this equipment. The definition of these symbols are as follows:

CautionText with a “CAUTION” indicator will explain possible safety infractions that could have the potential to cause minor to moderate injury or damage to equipment.

DangerText with a “DANGER” indicator will explain possible safety infractions that are imminently hazardous situations that would result in death or serious injury. Dangerous VoltageText with a “Dangerous Voltage” indicator serves to inform the user of possible hazards resulting in the electrical charge delivered to the patient in certain treatment configurations of TENS/NMES waveforms.

WarningText with a “WARNING” indicator will explain possible safety infractions that will potentially cause serious injury and equipment damage.

NOTE: Throughout this manual, “NOTE” may be found. These Notes are helpful information to aid in the particular area or function being described.

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SAFETY PRECAUTIONS

Intelect® Mobile Stim

CAUTIONS

• Read, understand, and practice the precautionary and

• The unit should be routinely checked before each use to

operating instructions. Know the limitations and hazards associated with using any electrical stimulation device. Observe the precautionary and operational decals placed on the unit. • DO NOT operate the Intelect Mobile Stim unit when connected to any unit other than Chattanooga Group devices. • DO NOT operate this unit in an environment where other devices are being used that intentionally radiate electromagnetic energy in an unshielded manner. • DO NOT use sharp objects such as a pencil point or ballpoint pen to operate the buttons on the control panel. • This unit should be operated, transported, and stored in temperatures between 15° C and 40° C (59° F and 104° F), with relative humidity ranging from 30%-60%, and where the atmospheric pressure is between 950 h Pa and 1050 h Pa.

determine that all controls function normally; especially that the intensity control properly adjusts the intensity of the electrotherapy power output in a stable manner. Also, determine that the treatment time control actually terminates electrotherapy power output when the timer reaches zero. • The Intelect battery pack is designed for use only with Chattanooga Group Intelect Mobile Stim, Combo, Laser, and Ultrasound systems. • Inspect cables and connectors before each use. • The Intelect Mobile Stim is not designed to prevent the ingress of water or liquids. Ingress of water or liquids could cause malfunction of internal components of the system and therefore create a risk of injury to the patient. • DO NOT permit any foreign materials or liquids to enter the unit. Take care to prevent any foreign materials including, but not limited to, inflammables, water, and metallic objects from entering the unit. These may cause unit damage, malfunction, electrical shock, fire, or personal injury.

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SAFETY PRECAUTIONS

Intelect® Mobile Stim

CAUTIONS CONTINUED

• The battery pack should be removed when storing the unit

• This equipment generates, uses and can radiate radio

for extended periods of time.

frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to other devices in the vicinity. However, there is no guarantee that interference will not occur in a particular installation. Harmful interference to other devices can be determined by turning this equipment on and off. Try to correct the interference using one or more of the following: reorient or relocate the receiving device, increase the separation between the equipment, connect the equipment to an outlet on a different circuit from that to which the other device(s) are connected and consult the factory field service technician for help. • Where the integrity of the external protective earth conductor arrangement is in doubt, equipment shall be operated from its internal electrical power source.

• DO NOT disassemble, modify, or remodel the unit or accessories. This may cause unit damage, malfunction, electrical shock, fire, or personal injury. • DO NOT remove the cover. This may cause unit damage, malfunction, electrical shock, fire, or personal injury. There are no user-serviceable parts inside the unit. If a malfunction occurs, discontinue use immediately and consult the dealer for repair service. • Failure to use and maintain the Intelect® Mobile Stim and its accessories in accordance with the instructions outlined in this manual will invalidate your warranty.

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SAFETY PRECAUTIONS

Intelect® Mobile Stim

WARNINGS

• These devices are restricted to sale by, or on the order of,

• TENS is a symptomatic treatment, and as such, suppresses the

a physician or licensed practitioner. This device should be used only under the continued supervision of a physician or licensed practitioner. • For continued protection against fire hazard, replace fuses only with ones of the same type and rating. • Make certain the unit is electrically grounded by connecting only to a grounded electrical service receptacle conforming to the applicable national and local electrical codes. • Care must be taken when operating this equipment around other equipment. Potential electromagnetic or other interference could occur to this or to the other equipment. Try to minimize this interference by not using other equipment in conjunction with it. • The safety of TENS waveforms for use during pregnancy or birth has not been established. • TENS is not effective for pain of central origin. (This includes headache.) • TENS should be used only under the continued supervision of a physician or licensed practitioner. • TENS waveforms have no curative value.

sensation of pain which would otherwise serve as a protective mechanism. • The user must keep the device out of the reach of children. • Electronic monitoring equipment (such as ECG monitors and ECG alarms) may not operate properly when TENS stimulation is in use. • Powered muscle stimulators should be used only with the leads and electrodes recommended for use by the manufacturer. • Before administering any treatment to a patient you should become acquainted with the operating procedures for each mode of treatment available, as well as the indications, contraindications, warnings, and precautions. Consult other resources for additional information regarding the application of Electrotherapy. • To prevent electrical shock, disconnect the unit from the power source before attempting any maintenance procedures. • Keep electrodes separated during treatment. Electrodes in contact with each other could result in improper stimulation or skin burns. • Long term effects of chronic electrical stimulation are unknown. 5

SAFETY PRECAUTIONS

Intelect® Mobile Stim

WARNINGS (continued)

• Stimulation should not be applied over the anterior neck or

• Use of controls or adjustments or performance of procedures

mouth. Severe spasm of the laryngeal and pharyngeal muscles may occur and the contractions may be strong enough to close the airway or cause difficulty in breathing. • Stimulation should not be applied transthoracically in that the introduction of electrical current into the heart may cause cardiac arrhythmia. • Stimulation should not be applied over swollen, infected, and inflamed areas or skin eruptions, e.g., phlebitis, thrombophlebitis, varicose veins, etc. • Stimulation should not be applied over, or in proximity to, cancerous lesions. • Output current density is inversely related to electrode size. Improper application may result in patient injury. If any question arises as to the proper electrode size, consult a licensed practitioner prior to therapy session. • Dispose of all products in accordance with local and national regulations and codes. • For continued protection against fire hazard, charge the battery pack only while installed on the Intelect Mobile Stim.

other than those specified herein may result in hazardous conditions causing damage to the battery pack or cells. • To prevent electrical shock, disconnect the battery pack from the system before attempting any maintenance procedures.

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SAFETY PRECAUTIONS

Intelect® Mobile Stim

DANGERS

• Stimulus delivered by the TENS waveforms of this

• DO NOT connect the unit to an electrical supply

device, in certain configurations, will deliver a charge of 25 microcoulombs (μC) or greater per pulse and may be sufficient to cause electrocution. Electrical current of this magnitude must not flow through the thorax because it may cause a cardiac arrhythmia. • Patients with an implanted neurostimulation device must not be treated with or be in close proximity to any shortwave diathermy, microwave diathermy, therapeutic ultrasound diathermy, or laser diathermy anywhere on their body. Energy from diathermy (shortwave, microwave, ultrasound, and laser) can be transferred through the implanted neurostimulation system, can cause tissue damage, and can result in severe injury or death. Injury, damage, or death can occur during diathermy therapy even if the implanted neurostimulation system is turned “off.”

without first verifying that the power supply is the correct voltage. Incorrect voltage may cause unit damage, malfunction, electrical shock, fire, or personal injury. Your unit was constructed to operate only on the electrical voltage specified on the Voltage Rating and Serial Number Plate. Contact your Chattanooga Group dealer if the unit is not properly rated. • NiMH Batteries contain Class E corrosive materials. In the event of battery cell rupture or leakage, handle battery pack wearing neoprene or natural rubber gloves. Contents of a ruptured or leaking battery can cause respiratory irritation. Hypersensitivity to nickel can cause allergic pulmonary asthma. Contents of cell coming in contact with skin can cause skin irritation and/or chemical burns. • Never, under any circumstances, open the battery pack housing or cells. Should an individual battery from a battery pack become disassembled, spontaneous combustion of the negative electrode is possible. There can be a delay between exposure to air and spontaneous combustion. 7

SAFETY PRECAUTIONS

Intelect® Mobile Stim

DANGERS CONTINUED

• Charge the battery pack according to the instructions found in this manual. Never attempt to charge the battery pack on any other charging mechanism. • Use the battery pack only with the Intelect Mobile Series units. • Do not reverse the polarity of the battery pack. Doing so can increase the individual cell temperature and cause cell rupture or leakage. • Never dispose of the battery pack in fire. Never short circuit the battery pack. The battery pack may explode, ignite, leak, or get hot causing serious personal injury. • Dispose of NiMH batteries according to national, state, and local codes and regulations.

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SAFETY PRECAUTIONS

Intelect® Mobile Stim

INDICATIONS, CONTRAINDICATIONS, AND ADVERSE EFFECTS • Other contraindications are patients suspected of carrying serious Indications for VMS, Russian, TENS, High Voltage Pulsed infectious disease and or disease where it is advisable, for general Current (HVPC), 2 Pole IFC, 4 Pole IFC and Premodulated medical purposes, to suppress heat or fevers. Waveforms • Relaxation of muscle spasms • Electrode placements must be avoided that apply current to the carotid sinus region (anterior neck) or transcereberally (through • Prevention or retardation of disuse atrophy the head). • Increase local blood circulation • Safety has not been established for the use of therapeutic • Muscle re-education electrical stimulation during pregnancy. • Maintaining or increasing range of motion • Powered muscle stimulators should not be used on patients with Additional Indications for Microcurrent, 2 Pole IFC, 4 Pole IFC, cardiac demand pacemakers. Premodulated, VMS™, and TENS Waveforms • There should not be any use of TENS waveforms on patients with • Symptomatic relief of management of chronic, intractable pain cardiac demand pacemakers. • Post-traumatic acute pain Additional Precautions • Post-surgical acute pain • Caution should be used for patients with suspected or diagnosed heart problems. Indications for Galvanic Continuous Mode • Relaxation of muscle spasm • Caution should be used for patients with suspected or diagnosed epilepsy. Contraindications • Caution should be used in the presence of the following: When • This device should not be used for symptomatic local pain there is a tendency to hemorrhage following acute trauma or relief unless etiology is established or unless a pain syndrome fracture; Following recent surgical procedures when muscle has been diagnosed. contraction may disrupt the healing process; Over a menstruating • This device should not be used when cancerous lesions are or pregnant uterus; Over areas of the skin which lack normal present in the treatment area. sensation. • This device should not be used when open wounds are present in the treatment area.

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SAFETY PRECAUTIONS

Intelect® Mobile Stim

INDICATIONS, CONTRAINDICATIONS, AND ADVERSE EFFECTS (continued)

• Some patients may experience skin irritation or hypersensitivity due to the electrical stimulation or electrical conductive medium. The irritation can usually be reduced by using an alternative conductive medium or an alternative electrode placement. • Electrode placement and stimulation settings should be based on the guidance of the prescribing practitioner. • Powered muscle stimulators should be used only with the lead wires and electrodes recommended for use by the manufacturer. • With TENS waveforms, isolated cases of skin irritation may occur at the site of electrode placement following long-term application. • The effectiveness of TENS waveforms is highly dependent upon patient selection by a person qualified in the management of pain patients. Adverse Effects • Skin irritation and burns beneath the electrodes have been reported with the use of powered muscle stimulators. • Potential adverse effects with TENS are skin irritation and electrode burns.

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OVERVIEW

Intelect® Mobile Stim

The Intelect Mobile Stim, designed and manufactured by Chattanooga Group, offers a new dimension in portable electrotherapy made possible by advanced software design and digital signal processing. The result is a unit with extraordinary versatility based on simplicity of operation. The Intelect Mobile Stim offers "On the Go" clinical electrotherapy. The unit provides an innovative case design, with a logical control system and a large, easy to read graphical LCD. User defined protocols allow you to customize any electrotherapy treatment to the specific needs of your patient. The repositional base allows the unit to be configured for desktop or wall-mount use. The following features are available on the Intelect Mobile Stim: • Two channels of electrotherapy stimulation output • Independent intensity and parameter controls for each channel • Eleven currents - 2 & 4 Pole IFC, Galvanic, High Voltage Pulsed Current (HVPC), Microcurrent, VMS, TENS, Russian, Träbert, Monophasic, and Diadynamic • Fifteen user-defined memory positions • Lightweight design • Battery powered option

Common Terms Accommodation - condition where nerves lose their ability (sensitivity) to respond to electrotherapy. Amplitude Modulation (Ampl. Mod.) - Amplitude Modulation is an increase and decrease in intensity during treatment. For example, at an 80% amplitude modulation, with the intensity set to 10 mA, the intensity decreases to 2 mA, and then increases to 10 mA throughout the treatment. The available amplitude modulations are 40%, 60%, 80%, 100%, and Static (none). Beat Fixed - Associated with the Interferential waveform, Beat Fixed is the parameter at which the beat frequency remains constant. When the Sweep setting is turned off, you must select a fixed beat for the therapy session. The available settings for Beat Fixed are 1 to 100 Hz. Beat Frequency - Associated with the Interferential waveform, Beat Frequency is the frequency at which the amplitude of the current increases and decreases. The beat frequency is considered to be the therapeutic frequency and is measured in hertz (Hz). 11

OVERVIEW

Intelect® Mobile Stim

Beat High - During a sweep, the Beat High setting is the highest number to which the beat frequency increases. The available range for the Beat High parameter is 2 to 200 Hz. This parameter is unique to the 2 Pole and 4 Pole IFC waveforms. Beat Low - During a sweep, the Beat Low setting is the lowest number to which the beat frequency decreases. The available range for the Beat Low parameter is 1 to 199 Hz. This parameter is unique to the 2 Pole and 4 Pole IFC waveforms. Burst - A burst is a series of pulses at a predetermined pulse frequency. Burst Frequency (Freq.) - This is the number of bursts per second (bps). The available burst frequencies on the Intelect Mobile Stim are 1 to 10 bps. Carrier Frequency (Freq.) - Associated with the Interferential and Russian waveforms, Carrier Frequency is the frequency of the unmodulated medium frequency current. The available carrier frequencies are 2000, 2500, 4000, 5000, and 10000 Hz. CC/CV - This is the abbreviation for Constant Current/Constant Voltage. Constant current is a stimulator capable of delivering an electric current that flows at the same amplitude regardless of changes in tissue impedance over time. Constant voltage is a stimulator capable of delivering a source of voltage at the same amplitude regardless of changes in tissue impedance over time. Most modern electrotherapy units are of the constant current type because they provide a consistent, or stable level of current amplitude throughout the therapy session, thus making it comfortable for the patient and predictable for the clinician. Keep in mind that the amount of stimulation is directly proportional to the current. Channel Mode - The available channel modes are Single Channel (in which electrotherapy is distributed from one channel), Reciprocal (where electrotherapy alternates between channels), and Co-Contract (where electrotherapy is distributed from both channels at the same time). Cycle Time - Cycle Time is the alternating time which the current is "on" and "off." Using the 10/30 setting as an example, the current is on for 10 seconds and off for 30. The available cycle times are Continuous, 5/5, 4/12, 10/10, 10/20, 10/30, and 10/50. Display - Available only on the High Volt waveform, the Display feature allows you to change the displayed Intensity parameter from Volts to Peak Current (Amps).

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OVERVIEW

Intelect® Mobile Stim

Duty Cycle - This is the ratio of the “On” time to “Total” time of the cycle, expressed as a percentage. The duty cycle describes the pulsed modes of electric stimulation. The lower the percentage, the lower temporal average intensity. 100% is continuous electrotherapy. The available Duty Cycles are 10, 20, 30, 40, 50%. Frequency - Frequency is the number of times per second a pulse, cycle, burst, or beat will repeat itself. The unit is selectable from 0-200 Hz (beat), 20-100 Hz (burst), and 2000-10000 Hz (carrier). Frequency Modulation (Freq. Mod.) - This is the rhythm at which a frequency changes. The available frequency modulations are 0 to 250 Hz in increments of 5 Hz. Intensity - Intensity is the output of electrotherapy distributed by the unit to the patient. Depending on the waveform, intensity is measured in milliamps (mA), volts (V), and micro amps (μa). Leadwires - The leadwires consist of the main plugs that are connected to the unit, and 4 leads (2 black and 2 red) that connect to electrodes. Medium Frequency Current - These are the currents used by the Traditional Interferential (IFC 4-Pole), Interferential Premodulated, and Russian waveforms that is higher than 1000 Hz, but lower than 10000 Hz. Operating Channels - Operating Channels are the paths by which the electrotherapy is distributed from the unit to the patient. The unit provides two channels of electrical stimulation. Phase Duration - This is the time in which the current flows in one direction only. Phase duration is the determined period of time elapsing from the beginning to the end of one phase, usually expressed in microseconds (μsec) or milliseconds (ms). Phase Interval - Available only with the Monophasic waveforms, it is the brief interruption of current flow between the individual phases of a pulse. The available phase intervals are 5 to 5000 ms in increments of 5 ms. Polarity - Polarity refers to the charge of an individual lead: positive or negative. Polarity Reversal - This is a feature available on the unit in which the polarity changes at a determined time. Pulsed Mode – This is an available mode on the unit in which electrotherapy is distributed intermittently.

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OVERVIEW

Intelect® Mobile Stim

Ramp - Ramp is the gradual increase and decrease in current. The purpose of ramping up the current is to maximize patient comfort by preventing the abrupt and sudden exposure to the current. Sweep - This is the modulation of therapeutic frequency commonly used to prevent accommodation. Sweeps are measured in pulses per second (pps) and Hertz (Hz). The available sweeps are 1-120 pps and 1-10 pps. Treatment Time – Measured in minutes and seconds, it is the suggested time in which therapy is given. Type - Displayed as a parameter on the unit, Type is used to signify the specific kind of waveform. For example, there are two types of Monophasic waveforms available on the unit: Monophasic Rectangular and Monophasic Triangular. Vector - A vector is a geometrically descriptive feature used to increase the effective therapeutic current at the crossing point of Traditional Interferential (IFC 4-Pole). Vector Position - The available vector positions are 0 to 90 degrees. Vector Scan - Measured in percentages, vector scans are the rhythmic changes of the position of vector. The available vector scans are Manual, Auto 40%, and Auto 100%. Waveforms - Waveforms are current or voltage that is varied by time and are the geometrical descriptions of a DC, AC, or pulsed DC/AC current. Current waveforms are described as either monophasic or biphasic. A biphasic wave is further described as either symmetrical or asymmetrical and as balanced or unbalanced. For more specifications and types of waveforms available on the Intelect Mobile Stim, refer to the section entitled "Waveform Specifications."

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NOMENCLATURE

Intelect® Mobile Stim

Power On/Off

LCD Intensity/ Contrast Dial

LCD

Up Arrow

Clinical Resources INTENSITY TIME

Parameter Display/Enter Channel 1 Lead Wire Connection

Back

START STOP Down Arrow

PAUSE Accessory Panel 15

Channel 2 Lead Wire Connection

NOMENCLATURE

Intelect® Mobile Stim

Power On/Off The Power On/Off button controls the flow of electricity to the unit. NOTE: Make certain there are no electrodes on the patient when turning the unit on or off.

LCD The LCD (Liquid Crystal Display) allows the user to view and monitor the information displayed before, during, and after therapy.

Clinical Resources Select this button to access the following functions: • Retrieving User Protocols • Restoring Factory Settings • Restoring Factory Protocols • Changing Languages • Viewing Unit Information Use the Up and Down Arrow buttons to navigate through the available options.

TIME Press the Up or Down arrow buttons to set total treatment time of therapy.

Back Use this button to return to the previous window.

STOP Select this button to stop a treatment session.

Down Arrow When the window displays a list of options, press the Down Arrow button to scroll down the list.

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NOMENCLATURE

Intelect® Mobile Stim

PAUSE Use this button to pause the treatment session. When pressed, the icon displays. To restart therapy, press the PAUSE button.

Accessory Panel The Accessory Panel serves as a port of connection for the electrodes.

Channel 1 Lead Wire Connection This port serves as the connection point between the unit and the Channel 1 Lead Wire.

Channel 2 Lead Wire Connection This port serves as the connection point between the unit and the Channel 2 Lead Wire.

START Select Start to begin a treatment session.

Parameter Display/Enter Select this button to display the parameters of the waveform during treatment. Also, this button is used to accept the highlighted selection.

INTENSITY Use the up or down arrow to increase or decrease output power dosage.

Up Arrow When the window displays a list of options, press the Up Arrow button to scroll up the list.

Battery Indicator When displayed on the LCD, this symbol indicates the battery pack option is present on the unit. This symbol also displays the charge status of the battery.

LCD Intensity/Contrast Dial If the intensity of the LCD display diminishes, turn the dial until the display contrast is optimal. 17