Sharp MX-B427PW User manual

LASER PRINTER
MX-B427PW
User's Guide
November 2020
Machine type(s):
4601
Models:
480 and its equivalent models

Contents
Safety information........................................................................................ 4
Conventions.......................................................................................................................................................... 4
Product statements............................................................................................................................................. 4
Learn about the printer................................................................................ 7
Printer configuration............................................................................................................................................7
Using the control panel...................................................................................................................................... 7
Understanding the status of the indicator light........................................................................................... 8
Selecting paper.................................................................................................................................................... 8
Set up, install, and configure..................................................................... 14
Selecting a location for the printer................................................................................................................ 14
Attaching cables................................................................................................................................................. 15
Installing optional trays..................................................................................................................................... 15
Loading paper and specialty media.............................................................................................................. 16
Installing and updating software, drivers, and firmware.........................................................................20
Networking...........................................................................................................................................................21
Configuring the SMTP server.........................................................................................................................23
Printing the Menu Settings Page...................................................................................................................23
Secure the printer.......................................................................................24
Locating the security slot................................................................................................................................ 24
Erasing printer memory................................................................................................................................... 24
Restoring factory default settings................................................................................................................. 24
Statement of Volatility...................................................................................................................................... 25
Print.............................................................................................................. 26
Printing from a computer.................................................................................................................................26
Printing from a mobile device........................................................................................................................ 26
Configuring confidential jobs......................................................................................................................... 27
Printing confidential and other held jobs....................................................................................................28
Printing a font sample list................................................................................................................................29
Placing separator sheets between copies................................................................................................. 29
Canceling a print job........................................................................................................................................ 29
Adjusting toner darkness................................................................................................................................ 29
Contents 2

Use printer menus...................................................................................... 30
Menu map........................................................................................................................................................... 30
Device.................................................................................................................................................................. 30
Print....................................................................................................................................................................... 38
Paper.....................................................................................................................................................................43
Network/Ports.....................................................................................................................................................45
Security.................................................................................................................................................................57
Reports..................................................................................................................................................................61
Troubleshooting.................................................................................................................................................62
Maintain the printer....................................................................................63
Checking the status of parts and supplies................................................................................................. 63
Configuring supply notifications....................................................................................................................63
Setting up e‑mail alerts....................................................................................................................................63
Viewing reports..................................................................................................................................................64
Ordering parts and supplies...........................................................................................................................64
Replacing parts and supplies......................................................................................................................... 64
Cleaning the printer.......................................................................................................................................... 75
Saving energy and paper................................................................................................................................76
Moving the printer to another location........................................................................................................ 76
Shipping the printer...........................................................................................................................................77
Troubleshoot a problem.............................................................................78
The printer is not responding.........................................................................................................................78
Network connection problems...................................................................................................................... 79
Issues with supplies...........................................................................................................................................81
Clearing jams.......................................................................................................................................................81
Paper feed problems........................................................................................................................................96
Printing problems.............................................................................................................................................. 99
Contacting your dealer....................................................................................................................................119
Notices........................................................................................................120
Index........................................................................................................... 128
Contents 3

Safety information
Conventions
Note: A note identifies information that could help you.
Warning: A warning identifies something that could damage the product hardware or software.
CAUTION: A caution indicates a potentially hazardous situation that could injure you.
Dierent types of caution statements include:
CAUTION—POTENTIAL INJURY: Indicates a risk of injury.
CAUTION—SHOCK HAZARD: Indicates a risk of electrical shock.
CAUTION—HOT SURFACE: Indicates a risk of burn if touched.
CAUTION—TIPPING HAZARD: Indicates a crush hazard.
CAUTION—PINCH HAZARD: Indicates a risk of being caught between moving parts.
Product statements
CAUTION—POTENTIAL INJURY: To avoid the risk of fire or electrical shock, connect the power cord to
an appropriately rated and properly grounded electrical outlet that is near the product and easily
accessible.
CAUTION—POTENTIAL INJURY: To avoid the risk of fire or electrical shock, use only the power cord
provided with this product or the manufacturer's authorized replacement.
CAUTION—POTENTIAL INJURY: Do not use this product with extension cords, multioutlet power strips,
multioutlet extenders, or UPS devices. The power capacity of these types of accessories can be easily
overloaded by a laser printer and may result in a risk of fire, property damage, or poor printer
performance.
CAUTION—POTENTIAL INJURY: Do not use this product with an inline surge protector. The use of a
surge protection device may result in a risk of fire, property damage, or poor printer performance.
CAUTION—SHOCK HAZARD: To avoid the risk of electrical shock, do not place or use this product near
water or wet locations.
CAUTION—SHOCK HAZARD: To avoid the risk of electrical shock, do not set up this product or make
any electrical or cabling connections, such as the power cord, fax feature, or telephone, during a
lightning storm.
CAUTION—POTENTIAL INJURY: Do not cut, twist, bind, crush, or place heavy objects on the power
cord. Do not subject the power cord to abrasion or stress. Do not pinch the power cord between objects
such as furniture and walls. If any of these things happen, a risk of fire or electrical shock results. Inspect
the power cord regularly for signs of such problems. Remove the power cord from the electrical outlet
before inspecting it.
Safety information 4

CAUTION—SHOCK HAZARD: To avoid the risk of electrical shock, make sure that all external
connections (such as Ethernet and telephone system connections) are properly installed in their marked
plug-in ports.
CAUTION—SHOCK HAZARD: To avoid the risk of electrical shock, if you are accessing the controller
board or installing optional hardware or memory devices sometime after setting up the printer, then turn
the printer o, and unplug the power cord from the electrical outlet before continuing. If you have any
other devices attached to the printer, then turn them o as well, and unplug any cables going into the
printer.
CAUTION—SHOCK HAZARD: To avoid the risk of electrical shock when cleaning the exterior of the
printer, unplug the power cord from the electrical outlet and disconnect all cables from the printer before
proceeding.
CAUTION—POTENTIAL INJURY: If the printer weight is greater than 20 kg (44 lb), then it may require
two or more people to lift it safely.
CAUTION—POTENTIAL INJURY: When moving the printer, follow these guidelines to avoid personal
injury or printer damage:
•Make sure that all doors and trays are closed.
•Turn o the printer, and then unplug the power cord from the electrical outlet.
•Disconnect all cords and cables from the printer.
•If the printer has separate floor-standing optional trays or output options attached to it, then disconnect
them before moving the printer.
•If the printer has a caster base, then carefully roll it to the new location. Use caution when passing over
thresholds and breaks in flooring.
•If the printer does not have a caster base but is configured with optional trays or output options, then remove
the output options and lift the printer o the trays. Do not try to lift the printer and any options at the same
time.
•Always use the handholds on the printer to lift it.
•Any cart used to move the printer must have a surface able to support the full footprint of the printer.
•Any cart used to move the hardware options must have a surface able to support the dimensions of the
options.
•Keep the printer in an upright position.
•Avoid severe jarring movements.
•Make sure that your fingers are not under the printer when you set it down.
•Make sure that there is adequate clearance around the printer.
CAUTION—TIPPING HAZARD: Installing one or more options on your printer or MFP may require a
caster base, furniture, or other feature to prevent instability causing possible injury. For more information
on supported configurations, contact the place where you purchased the printer.
CAUTION—TIPPING HAZARD: To reduce the risk of equipment instability, load each tray separately.
Keep all other trays closed until needed.
CAUTION—HOT SURFACE: The inside of the printer might be hot. To reduce the risk of injury from a hot
component, allow the surface to cool before touching it.
CAUTION—PINCH HAZARD: To avoid the risk of a pinch injury, use caution in areas marked with this
label. Pinch injuries may occur around moving parts, such as gears, doors, trays, and covers.
Safety information 5

CAUTION—POTENTIAL INJURY: This product uses a laser. Use of controls or adjustments or
performance of procedures other than those specified in the User’s Guide may result in hazardous
radiation exposure.
CAUTION—POTENTIAL INJURY: The lithium battery in this product is not intended to be replaced.
There is a danger of explosion if a lithium battery is incorrectly replaced. Do not recharge, disassemble,
or incinerate a lithium battery. Discard used lithium batteries according to the manufacturer's instructions
and local regulations.
This product is designed, tested, and approved to meet strict global safety standards with the use of specific
manufacturer's components. The safety features of some parts may not always be obvious. The manufacturer
is not responsible for the use of other replacement parts.
Refer service or repairs, other than those described in the user documentation, to a service representative.
This product uses a printing process that heats the print media, and the heat may cause the media to release
emissions. You must understand the section in your operating instructions that discusses the guidelines for
selecting print media to avoid the possibility of harmful emissions.
This product may produce small amounts of ozone during normal operation, and may be equipped with a filter
designed to limit ozone concentrations to levels well below the recommended exposure limits. To avoid high
ozone concentration levels during extensive usage, install this product in a well-ventilated area and replace
the ozone and exhaust filters if instructed to do so in the product maintenance instructions. If there are no
references to filters in the product maintenance instructions, then there are no filters requiring replacement for
this product.
SAVE THESE INSTRUCTIONS.
Safety information 6

Learn about the printer
Printer configuration
1Control panel
2Multipurpose feeder
3Standard 250‑sheet tray
4Optional 550‑sheet tray
5Standard bin
Using the control panel
Control panel part Function
1Display •View printer messages and supply status.
•Set up and operate the printer.
Learn about the printer 7

Control panel part Function
2Right arrow button •Scroll through menus or move between screens and menu options.
•Increase the numeric value of a setting.
3Stop or Cancel button Stop the current job.
4Indicator light Check the status of the printer.
5Select button •Select a menu option.
•Save the changes in a setting.
6Back button Return to the previous screen.
7Left arrow button •Scroll through menus or move between screens and menu options.
•Decrease the numeric value of a setting.
8Power button Turn on or turn o the printer.
Note: To turn o the printer, press and hold the power button for five seconds.
Understanding the status of the indicator light
Indicator light Printer status
O The printer is o or in Hibernate mode.
Blue The printer is ready or processing data.
Blinking red The printer requires user intervention.
Solid amber The printer is in Sleep mode.
Selecting paper
Paper guidelines
Use the appropriate paper to prevent jams and help ensure trouble‑free printing.
•Always use new, undamaged paper.
•Before loading paper, know the recommended printable side of the paper. This information is usually
indicated on the paper package.
•Do not use paper that has been cut or trimmed by hand.
•Do not mix paper sizes, types, or weights in the same tray; mixing results in jams.
•Do not use coated papers unless they are specifically designed for electrophotographic printing.
Paper characteristics
The following paper characteristics aect print quality and reliability. Consider these factors before printing on
them.
Learn about the printer 8

Weight
The standard tray can feed paper weights from 60 to 120 g/m2(16 to 32 lb) grain long paper. Paper lighter than
60 g/m2(16 lb) may not be sti enough to feed properly, and may cause jams.
Curl
Curl is the tendency for paper to curl at its edges. Excessive curl can cause paper feeding problems. Curl can
occur after the paper passes through the printer, where it is exposed to high temperatures. Storing paper
unwrapped in hot, humid, cold, or dry conditions can contribute to paper curling before printing and can cause
feeding problems.
Smoothness
Paper smoothness directly aects print quality. If paper is too rough, toner cannot fuse to it properly. If paper
is too smooth, it can cause paper feeding or print quality issues. We recommend the use of paper with 50
Sheeld points.
Moisture content
The amount of moisture in paper aects both print quality and the printer ability to feed the paper correctly.
Leave paper in its original wrapper until you use it. Exposure of paper to moisture changes can degrade its
performance.
Store paper in its original wrapper in the same environment as the printer for 24 to 48 hours before printing.
Extend the time several days if the storage or transportation environment is very dierent from the printer
environment. Thick paper may also require a longer conditioning period.
Grain direction
Grain refers to the alignment of the paper fibers in a sheet of paper. Grain is either grain long, running the length
of the paper, or grain short, running the width of the paper.
For 60–120 g/m2(16–32‑lb) paper, grain long paper is recommended.
Fiber content
Most high‑quality xerographic paper is made from 100 percent chemically treated pulped wood. This content
provides the paper with a high degree of stability, resulting in fewer paper feeding problems and better print
quality. Paper containing fibers such as cotton can negatively aect paper handling.
Unacceptable paper
The following paper types are not recommended for use with the printer:
•Chemically treated papers used to make copies without carbon paper, also known as carbonless papers,
carbonless copy paper (CCP), or no carbon required (NCR) paper
•Preprinted papers with chemicals that may contaminate the printer
•Preprinted papers that can be aected by the temperature in the printer fuser
•Preprinted papers that require a registration (the precise print location on the page) greater than ±2.3 mm
(±0.9 in.), such as optical character recognition (OCR) forms
In some cases, registration can be adjusted with a software application to successfully print on these forms.
•Coated papers (erasable bond), synthetic papers, thermal papers
Learn about the printer 9

•Rough‑edged, rough or heavily textured surface papers, or curled papers
•Recycled papers that fail EN12281:2002 (European)
•Paper weighing less than 60 g/m2(16 lb)
•Multiple‑part forms or documents
Selecting preprinted forms and letterhead
•Use grain long paper.
•Use only forms and letterhead printed using an oset lithographic or engraved printing process.
•Avoid paper with rough or heavily textured surfaces.
•Use inks that are not aected by the resin in toner. Inks that are oxidation‑set or oil‑based generally meet
these requirements; latex inks might not.
•Print samples on preprinted forms and letterheads considered for use before buying large quantities. This
action determines whether the ink in the preprinted form or letterhead aects print quality.
•When in doubt, contact your paper supplier.
•When printing on letterhead, load the paper in the proper orientation for your printer.
Storing paper
Use these paper storage guidelines to help avoid jams and uneven print quality:
•Store paper in its original wrapper in the same environment as the printer for 24 to 48 hours before printing.
•Extend the time several days if the storage or transportation environment is very dierent from the printer
environment. Thick paper may also require a longer conditioning period.
•For best results, store paper where the temperature is 21°C (70°F) and the relative humidity is 40 percent.
•Most label manufacturers recommend printing in a temperature range of 18–24°C (65–75°F) with relative
humidity between 40 and 60 percent.
•Store paper in cartons, on a pallet or shelf, rather than on the floor.
•Store individual packages on a flat surface.
•Do not store anything on top of individual paper packages.
•Take paper out of the carton or wrapper only when you are ready to load it in the printer. The carton and
wrapper help keep the paper clean, dry, and flat.
Learn about the printer 10

Supported paper sizes
Paper size Standard
250‑sheet
tray
Optional
550‑sheet
tray
Multipurpose
feeder
Two‑sided
printing
A4
210 x 297 mm
(8.27 x 11.7 in.)
A5 Portrait (SEF)
148 x 210 mm
(5.83 x 8.27 in.)
X
A5 Landscape (LEF)1
210 x 148 mm
(8.27 x 5.83 in.)
X
A6
105 x 148 mm
(4.13 x 5.83 in.)
X
JIS B5
182 x 257 mm
(7.17 x 10.1 in.)
X
Oficio (Mexico)
215.9 x 340.4 mm
(8.5 x 13.4 in.)
Hagaki
100 x 148 mm
(3.94 x 5.83 in.)
X X
Statement
139.7 x 215.9 mm
(5.5 x 8.5 in.)
X
Executive
184.2 x 266.7 mm
(7.25 x 10.5 in.)
X
Letter
215.9 x 279.4 mm
(8.5 x 11 in.)
1The default support is long‑edge feed.
2Paper must at least be 210 mm (8.27in.) wide and 279.4 mm (11 in.) long for two‑sided printing.
3When Universal is selected, the page is formatted for 215.90 x 355.60 mm (8.5 x 14 in.) unless specified by the
application.
Learn about the printer 11

Paper size Standard
250‑sheet
tray
Optional
550‑sheet
tray
Multipurpose
feeder
Two‑sided
printing
Legal
215.9 x 355.6 mm
(8.5 x 14 in.)
Folio
215.9 x 330.2 mm
(8.5 x 13 in.)
Universal3
99 x 148 mm to
215.9 x 359.92 mm
(3.9 x 5.83 in. to 8.5 x 14.17 in.)
2
7 3/4 Envelope
98.4 x 190.5 mm
(3.875 x 7.5 in.)
XX X
9 Envelope
98.4 x 225.4 mm
(3.875 x 8.9 in.)
XX X
10 Envelope
104.8 x 241.3 mm
(4.12 x 9.5 in.)
XX X
DL Envelope
110 x 220 mm
(4.33 x 8.66 in.)
XX X
C5 Envelope
162 x 229 mm
(6.38 x 9.01 in.)
XX X
B5 Envelope
176 x 250 mm
(6.93 x 9.84 in.)
XX X
Other Envelope
98.4 x 162 mm to
176 x 250 mm
(3.87 x 6.38 in. to
6.93 x 9.84 in.)
XX X
1The default support is long‑edge feed.
2Paper must at least be 210 mm (8.27in.) wide and 279.4 mm (11 in.) long for two‑sided printing.
3When Universal is selected, the page is formatted for 215.90 x 355.60 mm (8.5 x 14 in.) unless specified by the
application.
Learn about the printer 12

Supported paper types
Paper type Standard
250‑sheet
tray
Optional 550‑sheet
tray
Multipurpose feeder Two‑sided printing
Plain paper
Card stock X X X
Recycled
Paper labels*X
Bond
Letterhead
Preprinted
Colored Paper
Light Paper
Heavy Paper
Rough/Cotton
Envelope X X X
Rough envelope X X X
* One‑sided paper labels are supported for occasional use of less than 20 pages per month. Vinyl, pharmacy, or
two‑sided labels are not supported.
Supported paper weights
Standard 250‑sheet
tray
Optional 550‑sheet
tray
Multipurpose feeder Two‑sided printing
Paper weight 60–120 g/m2
(16–32 lb)
60–120 g/m2
(16–32 lb)
60–217 g/m2
(16–58 lb)
60–90 g/m2
(16–24 lb)
Learn about the printer 13

Set up, install, and configure
Selecting a location for the printer
•Leave enough room to open trays, covers, and doors and to install hardware options.
•Set up the printer near an electrical outlet.
CAUTION—POTENTIAL INJURY: To avoid the risk of fire or electrical shock, connect the power cord
to an appropriately rated and properly grounded electrical outlet that is near the product and easily
accessible.
CAUTION—SHOCK HAZARD: To avoid the risk of electrical shock, do not place or use this product
near water or wet locations.
•Make sure that airflow in the room meets the latest revision of the ASHRAE 62 standard or the CEN Technical
Committee 156 standard.
•Provide a flat, sturdy, and stable surface.
•Keep the printer:
–Clean, dry, and free of dust
–Away from stray staples and paper clips
–Away from the direct airflow of air conditioners, heaters, or ventilators
–Free from direct sunlight and humidity extremes
•Observe the recommended temperatures and avoid fluctuations.
Ambient temperature 10 to 32.2°C (50 to 90°F)
Storage temperature -40 to 40°C (-40 to 104°F)
•Allow the following recommended amount of space around the printer for proper ventilation:
1Top 30 5 mm ( 12 i n. )
2Rear 100 mm (3.94 in.)
3Right side 76.2 mm (3 in.)
Set up, install, and configure 14

4Front 305 mm (12 in.)
Note: The minimum space needed in front of the printer is 76 mm (3 in.).
5Left side 110 mm (4.33 in.)
Attaching cables
CAUTION—SHOCK HAZARD: To avoid the risk of electrical shock, do not set up this product or make
any electrical or cabling connections, such as the power cord, fax feature, or telephone, during a
lightning storm.
CAUTION—POTENTIAL INJURY: To avoid the risk of fire or electrical shock, connect the power cord to
an appropriately rated and properly grounded electrical outlet that is near the product and easily
accessible.
CAUTION—POTENTIAL INJURY: To avoid the risk of fire or electrical shock, use only the power cord
provided with this product or the manufacturer's authorized replacement.
Warning—Potential Damage: To avoid loss of data or printer malfunction, do not touch the USB cable, any
wireless network adapter, or the printer in the areas shown while actively printing.
Printer port Function
1USB printer port Connect the printer to a computer.
2Ethernet port Connect the printer to a network.
3Power cord socket Connect the printer to an electrical outlet.
Installing optional trays
CAUTION—SHOCK HAZARD: To avoid the risk of electrical shock, if you are accessing the controller
board or installing optional hardware or memory devices sometime after setting up the printer, then turn
the printer o, and unplug the power cord from the electrical outlet before continuing. If you have any
other devices attached to the printer, then turn them o as well, and unplug any cables going into the
printer.
1Turn o the printer.
2Unplug the power cord from the electrical outlet, and then from the printer.
3Unpack the optional tray, and then remove all packing material.
Set up, install, and configure 15

4Align the printer with the optional tray, and then lower the printer into place.
CAUTION—POTENTIAL INJURY: If the printer weight is greater than 20 kg (44 lb), then it may
require two or more people to lift it safely.
5Connect the power cord to the printer, and then to the electrical outlet.
CAUTION—POTENTIAL INJURY: To avoid the risk of fire or electrical shock, connect the power cord
to an appropriately rated and properly grounded electrical outlet that is near the product and easily
accessible.
6Turn on the printer.
Add the tray in the print driver to make it available for print jobs. For more information, see “Adding available
options in the print driver” on page 21.
Loading paper and specialty media
Setting the paper size and type
1From the control panel, navigate to:
Settings > > Paper > > Tray Configuration > > Paper Size/Type > > select a paper
source
2Set the paper size and type.
Configuring Universal paper settings
1From the control panel, navigate to:
Settings > > Paper > > Media Configuration > > Universal Setup >
2Configure the settings.
Loading trays
1Remove the tray.
Note: To avoid paper jams, do not remove the tray while the printer is busy.
Set up, install, and configure 16

2Adjust the guides to match the size of the paper that you are loading.
3Flex, fan, and align the paper edges before loading.
4Load the paper stack with the printable side facedown, and then make sure that the guides fit snugly against
the paper.
Notes:
•Load letterhead facedown with the header toward the front of the tray for one‑sided printing.
•Load letterhead faceup with the header toward the back of the tray for two‑sided printing.
•Do not slide paper into the tray.
•To avoid paper jams, make sure that the stack height is below the maximum paper fill indicator.
Set up, install, and configure 17

5Insert the tray.
If necessary, set the paper size and paper type from the control panel to match the paper loaded.
Loading the multipurpose feeder
1Open the multipurpose feeder.
2Flex, fan, and align the paper edges before loading.
Set up, install, and configure 18

3Load paper with the printable side faceup.
Notes:
•Load letterhead faceup with the header toward the rear of the printer for one‑sided printing.
•Load letterhead facedown with the header toward the front of the printer for two‑sided printing.
•Load envelopes with the flap facedown on the left side.
Warning—Potential Damage: Do not use envelopes with stamps, clasps, snaps, windows, coated linings,
or self‑stick adhesives.
4Adjust the guide to match the size of the paper that you are loading.
5From the control panel, set the paper size and paper type to match the paper loaded.
Linking trays
1From the control panel, navigate to:
Settings > > Paper > > Tray Configuration > > Paper Size/Type >
2Set the same paper size and paper type for the trays that you are linking.
3From the control panel, navigate to:
Settings > > Device > > Maintenance > > Config Menu > > Tray Configuration >
4Set Tray Linking to Automatic.
To unlink trays, make sure that no trays have the same paper size and paper type settings.
Warning—Potential Damage: The temperature of the fuser varies according to the specified paper type. To
avoid printing issues, match the paper type setting in the printer with the paper loaded in the tray.
Set up, install, and configure 19

Installing and updating software, drivers, and firmware
Installing the printer software
1Obtain a copy of the software installer package.
•From our website.
•From the place where you purchased the printer.
2Run the installer, and then follow the instructions.
3For Macintosh users, add the printer.
Note: For Macintosh computers with macOS version 10.7 or later, you do not need to install the driver to
print on an AirPrint-certified printer.
Updating firmware
Some applications require a minimum device firmware level to operate correctly.
For more information on updating the device firmware, contact your sales representative.
1Open a web browser, and then type the printer IP address in the address field.
Notes:
•View the printer IP address on the printer home screen. The IP address appears as four sets of
numbers separated by periods, such as 123.123.123.123.
•If you are using a proxy server, then temporarily disable it to load the web page correctly.
2Click Settings > Device > Update Firmware.
3Browse to the flash file.
4Click Upload.
Exporting or importing a configuration file
You can export the configuration settings of your printer into a text file, and then import the file to apply the
settings to other printers.
1Open a web browser, and then type the printer IP address in the address field.
Notes:
•View the printer IP address on the printer home screen. The IP address appears as four sets of
numbers separated by periods, such as 123.123.123.123.
•If you are using a proxy server, then temporarily disable it to load the web page correctly.
2From the Embedded Web Server, click Export Configuration or Import Configuration.
3Follow the instructions on the screen.
4If the printer supports applications, then do the following:
aClick Apps > select the application > Configure.
bClick Export or Import.
Set up, install, and configure 20