CMS50D1 - Pulse oximeter Contec - Free user manual and instructions

Product Type	Pulse Oximeter
Model	CMS50D1
Brand	Contec
Dimensions	61 (L) × 36 (W) × 32 (H) mm
Weight (with batteries)	Approximately 57 g
Power Supply	2 × 1.5V AAA alkaline batteries (or rechargeable)
Battery Life	Up to 20 hours continuous operation
Display	OLED display showing SpO₂, pulse rate, pulse bar graph, pulse waveform
SpO₂ Measuring Range	0% – 100%
SpO₂ Accuracy	±2% (70% – 100% SpO₂)
Pulse Rate Measuring Range	30 – 250 bpm
Pulse Rate Accuracy	±2 bpm or ±2% (whichever is larger)
Pulse Intensity Display	Bar-graph
Optical Sensor Wavelengths	Red: 660 nm; Infrared: 880 nm
Auto Power-Off	After 5 seconds without signal
Operating Environment	Temperature: 10°C – 40°C; Humidity: ≤75%; Pressure: 700 – 1060 hPa
Storage Environment	Temperature: -40°C – 60°C; Humidity: ≤95%; Pressure: 500 – 1060 hPa
Product Life	3 years
Accessories Included	Hanging rope, 2 batteries (optional), user manual
Cleaning & Disinfection	Wipe with medical alcohol; do not immerse; do not use high-pressure sterilization
Maintenance	Only qualified service engineers; periodic calibration recommended
Safety Precautions	Do not use near flammable gases, during MRI/CT, on infants/neonates, or for continuous monitoring; avoid prolonged use on same finger (>2 hours)
Classification	Class IIb (MDD 93/42/EEC), Class II (FDA)

Frequently Asked Questions - CMS50D1 Contec

How do I turn on the CMS50D1 pulse oximeter?

Insert two AAA batteries correctly, then press the button on the front panel once. The device will power on and start measuring. If no finger is inserted, it will automatically turn off after 5 seconds.

What should I do if the SpO₂ and pulse rate are not displayed?

Ensure the finger is properly positioned inside the clip with the fingernail facing the luminescent tube. If the reading is still absent, the patient's SpO₂ may be too low to detect. In that case, consult a healthcare professional.

How can I change the display orientation?

While the device is on, press the button briefly to rotate the screen 90 degrees. Each short press changes the direction.

How do I adjust the screen brightness?

With the device on, press and hold the button for a longer time to cycle through brightness levels.

Can I use the oximeter while charging?

No, the CMS50D1 runs on batteries only. It does not have a charging function. If using rechargeable batteries, remove them and charge externally.

How often should I clean the device?

Clean the surface before each use with a soft cloth dampened with medical alcohol. Allow it to air dry. Do not immerse in liquid or use high-pressure sterilization.

Is the oximeter suitable for children?

Yes, for children aged 4 years and older with a weight between 15 kg and 110 kg. It is not intended for infants or neonates.

What do the symbols on the screen mean?

The screen shows SpO₂ (%), pulse rate (bpm), a pulse bar graph, and a pulse waveform. A low battery icon appears when batteries need replacement. Refer to the manual for all symbol definitions.

How do I replace the batteries?

Open the battery cover on the back, remove old batteries, and insert two new AAA alkaline (or rechargeable) batteries with correct polarity. Close the cover. Remove batteries if storing for more than one month to prevent leakage.

Can the device be used with nail polish or artificial nails?

No, the patient should not wear nail enamel or other makeup on the finger being measured, as it may interfere with the optical sensor and cause inaccurate readings.

USER MANUAL CMS50D1 Contec

Line drawing of a rectangular electronic device with a screen and label 'CE 0123' (no text or symbols on the device itself)

CONTEC™ CONTEC MEDICAL SYSTEMS CO., LTD

Address: No.112 Qinhuang West Street, Economic & Technical Development Zone, Qinhuangdao, Hebei Province, PEOPLE'S REPUBLIC OF CHINA

Tel: [phone]

Fax: [phone]

Technical support: 0086-335-8015431

E-mail: [e-mail]

[e-mail]

Website: http://www.contecmed.com

Instructions to User

Dear Users, thank you very much for purchasing our product.

This Manual is written and compiled in accordance with the council directive MDD93/42/EEC for medical devices and harmonized standards. The Manual is written for the current Pulse Oximeter. In case of modifications and software upgrades, the information contained in this document is subject to change without notice.

The Manual describes, in accordance with the Pulse Oximeter's features and requirements, main structure, functions, specifications, correct methods for transportation, installation, usage, operation, repair, maintenance and storage, etc. as well as the safety procedures to protect both the user and equipment. Refer to the respective chapters for details.

Please read the Manual very carefully before using this equipment. These instructions describe the operating procedures to be followed strictly, failure to follow these instructions can cause measuring abnormality, equipment damage and personal injury. The manufacturer is NOT responsible for the safety, reliability and performance issues and any monitoring abnormality, personal injury and equipment damage due to user's negligence of the operation instructions. The manufacturer's warranty service does not cover such faults.

Owing to the forthcoming renovation, the specific products you received may not be totally in accordance with the description of this User Manual. We would sincerely regret for that.

This product is medical device, and can be used repeatedly. Its using life is 3 years.

WARNING:

The uncomfortable or painful feeling may appear if using the device ceaselessly, especially for the microcirculation barrier patients. It is recommended that the sensor should not be applied to the same finger for over 2 hours.

For the individual patients, there should be a more prudent inspecting in the placing process. The device can not be clipped on the edema and tender tissue.

The light (the infrared is invisible) emitted from the device is harmful to the eyes, so the user and the maintenance man, can not stare at the light.

Testee can not use enamel or other makeup.

Testee's fingernail can not be too long.

Please peruse the relative content about the clinical restrictions and caution.

This device is not intended for treatment.

The User Manual is published by our company. All rights reserved.

1 Safety

1.1 Instructions for Safe Operations

Check the main unit and all accessories periodically to make sure that there is no visible damage that may affect patient's safety and monitoring performance about cables and transducers. It is recommended that the device should be inspected once a week at least. When there is obvious damage, stop using the monitor.
➢ Necessary maintenance must be performed by qualified service engineers ONLY. Users are not permitted to maintain it by themselves.
The oximeter cannot be used together with devices not specified in User's Manual. Only the accessory that appointed or recommendatory by manufacture can be used with this device.
This product is calibrated before leaving factory.

1.2 Warnings

Explosive hazard—DO NOT use the oximeter in environment with inflammable gas such as some ignitable anesthetic agents.
➢DO NOT use the oximeter while the testee measured by MRI and CT.

EC REPRESENTATIVE

Shanghai International Holding Corp. GmbH(Europe)

Address: Eiffestrasse 80, 20537, Hamburg, Germany

Tel: [phone] Fax: [phone]

E-mail: [e-mail]

File No.: CMS2.782.178(CE.USA)ESS/1.4

Release Date: February 2014

1.4.01.01.222

The person who is allergic to rubber can not use this device.

The disposal of scrap instrument and its accessories and packings(including battery, plastic bags, foams and paper boxes) should follow the local laws and regulations.
Please check the packing before use to make sure the device and accessories are totally in accordance with the packing list, or else the device may have the possibility of working abnormally.
Please don't measure this device with function test paper for the device's related information.

1.3 Attentions

Keep the oximeter away from dust, vibration, corrosive substances, explosive materials, high temperature and moisture.
If the oximeter gets wet, please stop operating it.
When it is carried from cold environment to warm or humid environment, please do not use it immediately.
☐DO NOT operate keys on front panel with sharp materials.
High temperature or high pressure steam disinfection of the oximeter is not permitted. Refer to User Manual in the relative chapter for instructions of cleaning and disinfection.
Do not have the oximeter immersed in liquid. When it needs cleaning, please wipe its surface with medical alcohol by soft material. Do not spray any liquid on the device directly.
When cleaning the device with water, the temperature should be lower than 60^ C.
As to the fingers which are too thin or too cold, it would probably affect the normal measure of the patients' SpO_2 and pulse rate, please clip the thick finger such as thumb and middle finger deeply enough into the probe.

Do not use the device on infant or neonatal patients.

The product is suitable for children above four years old and adults(Weight should be between 15kg to 110kg).
The device may not work for all patients. If you are unable to achieve stable readings, discontinue use.
The update period of data is less than 5 seconds, which is changeable according to different individual pulse rate.
The waveform is normalized. Please read the measured value when the waveform on screen is equably and steady-going. Here this measured value is optimal value. And the waveform at the moment is the standard one.
If some abnormal conditions appear on the screen during test process, pull out the finger and reinsert to restore normal use.

The device has normal useful life for three years since the first electrified use.

The hanging rope attached the product is made from Non- allergy material, if particular group are sensitive to the hanging rope, stop using it. In addition, pay attention to the use of the hanging rope, do not wear it around the neck avoiding cause harm to the patient.
The instrument dose not have low-voltage alarm function, it only shows the low-voltage, please change the battery when the battery energy is used out.
When the parameter is particularly, The instrument dose not have alarm function. Do not use the device in situations where alarms are required.
Batteries must be removed if the device is going to be stored for more than one month, or else batteries may leak.
A flexible circuit connects the two parts of the device. Do not twist or pull on the connection.

2 Overview

The pulse oxygen saturation is the percentage of Hb 2 the total Hb in the blood, so-called the O concentration in the blood. It is an important bio-parameter for the respiration. For the purpose of measuring the SpO 2 more easily and accurately, our company developed the Pulse Oximeter. At the same time, the device can measure the pulse rate simultaneously.

The Pulse Oximeter features in small volume, low power consumption, convenient operation and being portable. It is only necessary for patient to put one of his fingers into a fingertip photoelectric sensor for diagnosis, and a display screen will directly show measured value of SpO_2 .

2.1 Classification:

Class II b(MDD93/42/EEC IX Rule 10)

Class II (U.S.FDA)

2.2 Features

➢Operation of the product is simple and convenient.

The product is small in volume, light in weight (total weight is about 50g including batteries) and convenient in carrying.
Power consumption of the product is low and the two originally equipped AAA batteries can be operated continuously for 20 hours.
The product will automatically be powered off when no signal is in the product within 5 seconds.

2.3 Major Applications and Scope of Application

The Pulse Oximeter can be used to measure human Hemoglobin Saturation and pulse rate through finger, and indicate the pulse intensity by the bar-display. The product is suitable for use in family, hospital(Ordinary sickroom), Oxygen Bar, social medical organizations and also the measure of saturation oxygen and pulse rate.

The product is not suitable for use in continuous supervision for patients.

The problem of overrating would emerge when ⚠ the patient is suffering from toxicosis which caused by carbon monoxide, the device is not recommended to be used under this circumstance.

2.4 Environment Requirements

Storage Environment

a) Temperature : -40 \~ +60°C°C
b) Relative humidity :≤95%
c) Atmospheric pressure :500hPa\~1060hPa

Operating Environment

a) Temperature: 10 40^^
b) Relative Humidity :≤75%
c) Atmospheric pressure:700hPa\~1060hPa

3 Principle and Caution

3.1 Principle of Measurement

Principle of the Oximeter is as follows: An experience formula of data process is established taking use of Lambert Beer Law according to Spectrum Absorption Characteristics of Reductive Hemoglobin (Hb) and Oxyhemoglobin (HbO_2) in glow & near-infrared zones. Operation principle of the instrument is: Photoelectric Oxyhemoglobin Inspection Technology is adopted in accordance with Capacity Pulse Scanning & Recording Technology, so that two beams of different wavelength of lights can be focused onto human nail tip through perspective clamp finger-type sensor. Then measured signal can be obtained by a photosensitive element, information acquired through which will be shown on screen through treatment in electronic circuits and microprocessor.

Figure 1. Operating Principle

3.2 Caution

1. The finger should be placed properly (see the attached illustration of this manual, Figure 5), or else it may cause inaccurate measurement.
2. The SpO_2 sensor and photoelectric receiving tube should be arranged in a way with the subject's arteriole in a position there between.
3. The SpO_2 sensor should not be used at a location or limb tied with arterial canal or blood pressure cuff or receiving intravenous injection.
4. Make sure the optical path is free from any optical obstacles like rubberized fabric.
5. Excessive ambient light may affect the measuring result. It includes fluorescent lamp, dual ruby light, infrared heater, direct sunlight and etc.
6. Strenuous action of the subject or extreme electrosurgical interference may also affect the accuracy.
7. Testee can not use enamel or other makeup.

3.3 Clinical Restrictions

1. As the measure is taken on the basis of arteriole pulse, substantial pulsating blood flow of subject is required. For a subject with weak pulse due to shock, low ambient/body temperature, major bleeding, or use of vascular contracting drug, the SpO_2 waveform (PLETH) will decrease. In this case, the measurement will be more sensitive to interference.
2. For those with a substantial amount of staining dilution drug (such as methylene blue, indigo green and acid

indigo blue), or carbon monoxide hemoglobin (COHb), or methionine (Me+Hb) or thiosalicylic hemoglobin, and some with icterus problem, the SpO_2 determination by this monitor may be inaccurate.

1. The drugs like dopamine, procaine, prilocaine, lidocaine and butacaine may also be a major factor blamed for serious error of SpO_2 measure.

2. As the SpO_2 value serves as a reference value for judgement of anemic anoxia and toxic anoxia, some patients with serious anemia may also report good SpO_2 measurement.

4 Technical Specifications

1. Display Format: OLED Display;

SpO_2 Measuring Range: 0% - 100% ;

Pulse Rate Measuring Range: 30 bpm - 250 bpm;

Pulse Wave Display: columniation display and the waveform display.

1. Power Requirements: 2 × 1.5V AAA alkaline battery (or using the rechargeable battery instead), adaptable range: 2.6V 3.6V .

2. Power Consumption: Smaller than 30mA.

3. Resolution: 1% for SpO_2 and 1 bpm for Pulse Rate.

4. Measurement Accuracy: ±2% in stage of 70%-100% SpO _2 , and meaningless when stage being smaller than 70%. ±2 bpm or ±2% (select larger) for Pulse Rate.

5. Measurement Performance in Weak Filling Condition: SpO_2 and pulse rate can be shown correctly when pulse-filling ratio is 0.4% . SpO_2 error is ± 4% , pulse rate error is ± 2 bpm or ± 2% (select larger).

6. Resistance to surrounding light: The deviation between the value measured in the condition of man-made light or indoor natural light and that of darkroom is less than ± 1% .

7. It is equipped with a function switch. The Oximeter can be powered off in case no finger is the Oximeter within 5 seconds.

9. Optical Sensor

Red light (wavelength is 660nm, 6.65mW)

Infrared (wavelength is 880nm, 6.75mW)

5 Accessories

One hanging rope;

▶ Two batteries (optional);

One User Manual.

6 Installation

6.1 View of the Front Panel

Figure 2. Front View

6.2 Battery

Step 1. Refer to Figure 3. and insert the two AAA size batteries properly in the right direction.

Step 2. Replace the cover.

Please take care when you insert the batteries ⚠️ for the improper insertion may damage the device.

Figure 3.

Batteries

Installation

6.3

Mounting

the

Hanging

Rope

Step 1. Put

the end of

the rope

through the hole.

Step 2. Put another end of the rope through the first one and then tighten it.

White digital pressure meter with attached black and blue connector (no visible text or symbols on device body)

7 Operating Guide

7.1 Insert the two batteries properly to the direction, and then replace the cover.
7.2 Open the clip as shown in Figure 5.

Figure 5. Put

finger in

position

7.3 Let the

patient's finger

put into the

rubber cushions

of the clip

(make sure the

finger is in the

right position),

and then clip the finger.

7.4 Press the switch button once on front panel.

7.5 Do not shake the finger and keep the patient at ease during the process. Meanwhile, human body is not recommended in movement status.

7.6 Get the information directly from screen display.

7.7 The button has three

functions. When the device is

power off, pressing the button can open it; When the device is power on, pressing the button shortly can change direction of the screen; When the device is power on, pressing the button long can change brightness of the screen.

Fingernails and the luminescent tube should be on the same side.

8 Repairing and

Maintenance

➢ Please change the batteries when the low-voltage displayed on the screen.
Please clean the surface of the device before using. Wipe the device with medical alcohol first, and then let it dry in air or clean it by dry clean fabric.
Using the medical alcohol to disinfect the product after use, prevent from cross infection for next time use.
➢ Please take out the batteries if the oximeter is not in use for a long time.
The best storage environment of the device is - 40°C to 60°C ambient temperature and not higher than 95% relative humidity.
Users are advised to calibrate the device termly (or according to the calibrating program of hospital). It also can be performed at the state-appointed agent or just contact us for calibration.

High-pressure sterilization cannot be used on the device.

Do not immerse the device in liquid.

It is recommended that the device should be ⚠️ kept in a dry environment. Humidity may reduce the useful life of the device, or even damage it.

9 Troubleshooting

Trouble	Possible Reason	Solution
The SpO_2 and Pulse Rate can not be displayed normally	1. The finger is not properly positioned.2. The patient's SpO_2 is too low to be detected.	1. Place the finger properly and try again.2. Try again; Go to a hospital for a diagnosis if you are sure the device works all right.
The SpO_2 and Pulse Rate are not displayed stably	1. The finger is not placed inside deep enough.2. The finger is shaking or the patient is moving.	1. Place the finger properly and try again.2. Let the patient keep calm

Blue circular icon with a white human figure using a laptop (no text or symbols)

Reference No.
ISO 7010-M002
Referent
Refer to instruction manual/booklet
Function
To signify that the instruction manual/booklet must be read
Image content
Upper human figure (right-hand profile) holding an open manual/booklet

Hazard

Not reading the instruction manual/booklet before starting work or before operating equipment or machinery Human behaviour that is intended to be caused after understanding the safety sign's meaning

Reading the Instruction manual/booklet before starting work or before operating equipment or machinery Related referents

-

Additional Information

Test data obtained according to ISO 9186-1:2007 are not available. Consequently, a supplementary text sign shall be used to increase comprehension except when the safety sign is supplemented by manuals, Instructions or training.

	Refer to instruction manual/booklet
%SpO2	The pulse oxygen saturation(%)
PRbpm	Pulse rate (bpm)
	The battery voltage indication is deficient (change the battery in time avoiding the inexact measure)
	1. no finger inserted2. An indicator of signal inadequacy
	battery positive electrode
	battery cathode
	1.Power switch2.change direction of the screen3.Change brightness of the screen
SN	Serial number
	Alarm inhibit
	WEEE (2002/96/EC)
IP22	Ingress of liquids rank
	European Representative
	This item is compliant with Medical Device Directive 93/42/EEC of June 14, 1993, a directive of the European Economic Community.

11 Function Specification

Display Information	Display Mode
The Pulse Oxygen Saturation(SpO2)	OLED
Pulse Rate(PR)	OLED
Pulse Intensity (bar-graph)	OLED bar-graph display
Pulse wave	OLED
SpO2Parameter Specification
Measuring range	0%~100%, (the resolution is 1%).
Accuracy	70%~100%: ±2%, Below 70% unspecified.
Optical Sensor	Red light (wavelength is 660nm)Infrared (wavelength is 880nm)
Pulse Parameter Specification
Measuring range	30bpm~250bpm (the resolution is 1 bpm)
Accuracy	±2bpm or±2% select larger
Pulse Intensity
Range	Continuous bar-graph display, the higher display indicate the stronger pulse.
Battery Requirement
1.5V (AAA size) alkaline batteries × 2 or rechargeable battery
Battery Useful Life
Two batteries can work continually for 20 hours
Dimensions and Weight
Dimensions	61(L) × 36(W) × 32(H) mm
Weight	About 57g (with the batteries)

Appendix

Guidance and manufacture's declaration-electromagnetic emission for all EQUIPMENT and SYSTEMS

Guidance and manufacture's declaration –electromagnetic emission
The CMS50D1 Pulse Oximeter is tended for use in the electromagnetic environment specified below. The customer of the user of the CMS50D1 Pulse Oximeter should assure that it is used in such an environment.
Emission test	compliance	Electromagnetic environment-guidance
RF emissions CISPR 11	Group 1	The CMS50D1 Pulse Oximeter uses RF energy only for their internal function. Therefore, its RF emissions are very low and are not likely to cause any interference in nearby electronic equipment.
RF emissions	Class B	The CMS50D1 Pulse Oximeter is suitable
CISPR 11 for use	in all establishments,including
Harmonic emissionsIEC 61000-3-2	Not applicable	domestic establishments and those directly connected to the public low-voltage power supply network that supplies buildings used for domestic purposes.
Voltage fluctuations/flicker emissionIEC 61000-3-3	Not applicable

Guidance and manufacture's declaration-electromagnetic immunity
for all EQUIPMENT and SYSTEMS

Guidance and manufacture's declaration-electromagnetic immunity
The CMS50D1 Pulse Oximeter is intended for use in the electromagnetic environment specified specified below. The the user of CMS50D1 Pulse Oximeter should assure that it is used in such an environment.
Immunity test IEC60601 test level Compliance level			Electromagnetic environment-guidance
Electrostatic discharge (ESD) IEC 61000-4-2	±6KV contact ±8KV air	±6KV contact ±8KV air	Floors should be wood, concrete or ceramic tile. If floor are covered with synthetic material, the relative humidity should be at least 30%.
Power frequency (50Hz) magnetic fieldIEC 61000-4-8	3A/m 3A/m Power frequency magnetic fields		should be at levels characteristic of a typical location in a typical commercial or hospital environment

Guidance and manufacture's declaration-electromagnetic immunity
for EQUIPMENT and SYSTEMS that are not LIFE-SUPPORTING

Guidance and manufacture's declaration-electromagnetic immunity
The CMS50D1 Pulse Oximeter is intended for use in the electromagnetic environment specified below. The customer or the user of CMS50D1 Pulse Oximeter should assure that it is used in such an environment.
Immunity test	IEC60601 test level	Compliance level	Electromagnetic environment -guidance
Radiated RF ICE 61000-4-3	3V/m80MHz to 2.5GHz	3V/m	Portable and mobile RF communication equipment should be used no closer to any part of the CMS50D1 Pulse Oximeter, including cables, than the recommended separation distance calculated from the equation applicable to the frequency of the transmitter.recommended separation distance80MHz to 800MHz800MHz d = [ 3.5E_1 ] 2.5GHz d = [ _1E_1 ] Where P is the maximum outputpower rating of the transmitter in watts (W) according to the transmitter manufacturer and d is the recommended separation distance in meters (m).Field strengths from fixed RF transmitters, as determined by an electromagnetic site survey, ^a should be less than the compliance level in each frequency range. ^b Interference may occur in the vicinity of equipment ma with the following symbol:
NOTE 1 At 80MHz and 800MHz, the higher frequency range applies.NOTE 2 These guidelines may not apply in all situations. Electr absorption and reflection from structures, objects and people.
^a Field strengths from fixed transmitters, such as base stations for radio (cellular/cordless) telephones and land mobile radios, amateur radio, AM and FM radio broadcast and TV broadcast cannot be pred theoretically with accuracy. To assess the electromagnetic environment due to fixed RF transmitters, an electromagnetic site survey should be considered. If the measured field strength in the location in which The CMS50D1 Pulse Oximeter is used exceeds the applicable RF compliance level above, the CMS50D1 Pulse Oximeter should be observed to verify normal operation. If abnormal performance is observed, additional measures may be necessary, such as reorienting or relocating the CMS50D1 Pulse Oximeter. ^b Over the frequency range 150 KHz to 80 MHz, field strengths should be less than 3V/m.

Recommended separation distances between portable and mobile

RF communications equipment and the EQUIPMENT or SYSTEM

for EQUIPMENT or SYSTEM that not LIFE-SUPPORTING

Recommended separation distances between portable and mobile RF communications equipment and the CMS50D1 Pulse Oximeter
The CMS50D1 Pulse Oximeter is intended for use in the electromagnetic environment in which radiated RF disturbances are controlled. The customer or the user of the CMS50D1 Pulse Oximeter can help prevent electromagnetic interference by maintaining a minimum distance between portable and mobile RF communications equipment (transmitters) and the CMS50D1 Pulse Oximeter as recommended below, according to the maximum output power of the communications equipment.
Rated maximum output power of transmitter (W)	Separation distance according to frequency of transmitter (m)
	d = [ 3.5E_1 ] 150KHz to 80MHz	d = [ 3.5E_1 ] 80MHz to 800MHz	800MHz to 2.5GHz d = [ 7E_1 ]
0.01	0.12	0.12	0.23
0.1	0.37	0.37	0.74
1	1.17	1.17	2.33
10	3.69	3.69	7.38
100	11.67	11.67	23.33
For transmitters rated at a maximum output power not listed above, the recommended separation distanced in meters (m) can be estimated using the equation applicable to the frequency of the transmitter, where P is the maximum output power rating of the transmitter in watts (W) according to the transmitter manufacturer.NOTE 1 At 80MHz and 800MHz, the separation distance for the higher frequency range applies.NOTE 2 These guidelines may not apply in all situations. Electromagnetic propagation is affected by absorption and reflection from structures, objects and people.