LINKSYS WVC54GV1 Wireless-G Video Camera User Manual Book
LINKSYS LLC Wireless-G Video Camera Book
LINKSYS >
Part 1
A Division of Cisco Systems, Inc.
®
Model No.
Internet Video Camera
Wireless-G
WVC54G V1.1
User Guide
WIRELESS
GHz
2.4
802.11g
Wireless-G Internet Video Camera
Copyright and Trademarks
Specifications are subject to change without notice. Linksys is a registered trademark or trademark of Cisco
Systems, Inc. and/or its affiliates in the U.S. and certain other countries. Copyright © 2004 Cisco Systems, Inc. All
rights reserved. Other brands and product names are trademarks or registered trademarks of their respective
holders.
How to Use this Guide
Your guide to the Wireless-G Internet Video Camera has been designed to make understanding networking with
the Camera easier than ever. Look for the following items when reading this guide:
In addition to these symbols, there are definitions for technical terms that are presented like this:
Also, each figure (diagram, screenshot, or other image) is provided with a figure number and description, like
this:
Figure numbers and descriptions can also be found in the “List of Figures” section in the “Table of Contents”.
This exclamation point means there is a Caution or
warning and is something that could damage your
property or the Camera.
word: definition.
This checkmark means there is a Note of interest and
is something you should pay special attention to while
using the Camera.
This question mark provides you with a reminder about
something you might need to do while using the Camera.
Figure 0-1: Sample Figure Description
WVC54G-UG-40420NC JL
Wireless-G Internet Video Camera
Table of Contents
Chapter 1: Introduction 1
Welcome 1
What’s in this Guide? 2
Chapter 2: Planning Your Wireless Network 4
Introduction 4
Ad-Hoc and Infrastructure Modes 4
Network Layout 4
Chapter 3: Getting to Know the Wireless-G Internet Video Camera 6
Camera LCD Screen and Built-in Microphone 6
Camera LEDs 6
Camera Head 6
Camera Ports 7
Chapter 4: Connecting the Wireless-G Internet Video Camera for Setup 8
Overview 8
Connection to a Wired Network for Setup 8
Connection to a Wireless Ad-Hoc Network for Setup 8
Moving the Camera to a Different Network 9
Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera 10
Setup Wizard 10
Placement Options 16
Audio Option 16
Chapter 6: Installing and Using the Wireless-G Internet Video Camera Viewer
& Recorder Utility 17
Overview 17
Installing the Viewer & Recorder Utility 17
Using the Viewer & Recorder Utility 19
Chapter 7: Setting up the Linksys SoloLink™ DDNS Service 30
Overview 30
Introduction 30
Setup Wizard for the SoloLink DDNS Service 30
SoloLink Registration of Additional Cameras 40
Wireless-G Internet Video Camera
Chapter 8: Using the Wireless-G Internet Video Camera’s Web-based Utility 42
Overview 42
How to Access the Web-based Utility 42
View Video 42
Setup 43
Help 54
Appendix A: Troubleshooting 56
Common Problems and Solutions 56
Frequently Asked Questions 59
Appendix B: Wireless Security 62
Security Precautions 62
Security Threats Facing Wireless Networks 62
Appendix C: Upgrading Firmware 64
Appendix D: Windows Help 65
Appendix E: Glossary 66
Appendix F: Specifications 73
Appendix G: Warranty Information 75
Appendix H: Regulatory Information 76
Appendix I: Contact Information 79
Wireless-G Internet Video Camera
List of Figures
Figure 3-1: Camera LCD Screen and Built-in Microphone 6
Figure 3-2: Camera LEDs 6
Figure 3-3: Camera Head 6
Figure 3-4: Camera Ports 7
Figure 4-1: Connect the Ethernet Network Cable 8
Figure 4-2: Connect the Power Adapter 8
Figure 5-1: Setup Wizard - Welcome Screen 10
Figure 5-2: Connection for Setup Screen 10
Figure 5-3: Cameras Found Screen 11
Figure 5-4: Login Screen 11
Figure 5-5: Basic Settings Screen 11
Figure 5-6: Network Settings Screen 12
Figure 5-7: IP Settings Screen 12
Figure 5-8: Mode Settings Screen 13
Figure 5-9: Wireless Settings Screen 13
Figure 5-10: Security Settings Screen 14
Figure 5-11: Review New Settings Screen 14
Figure 5-12: Confirmation Screen 15
Figure 5-13: Congratulations Screen 15
Figure 5-14: Stand Option 16
Figure 5-15: Camera Desktop Stand 16
Figure 5-16: Wall Mount Option 16
Figure 5-17: Wall-Mount Slots 16
Figure 6-1: Install Viewer & Recorder Utility Screen 17
Figure 6-2: Install Viewer & Recorder Utility - Welcome Screen 17
Figure 6-3: Choose Destination Location Screen 18
Figure 6-4: Select Program Folder Screen 18
Figure 6-5: OCX Plug-in Screen 18
Wireless-G Internet Video Camera
Figure 6-6: Setup Complete Screen 18
Figure 6-7: Viewer & Recorder Utility Icon 19
Figure 6-8: Main Screen 19
Figure 6-9: Find Camera from LAN Screen 20
Figure 6-10: Camera Added Successfully Screen 20
Figure 6-11: Find Camera from Internet Screen 21
Figure 6-12: Change Settings Screen 21
Figure 6-13: Delete Camera Screen 22
Figure 6-14: Confirm Deletion of Camera Screen 22
Figure 6-15: View Video Screen 23
Figure 6-16: Recording Icon Screen 23
Figure 6-17: Scheduled Recordings in Progress Screen 26
Figure 6-18: Files Screen 26
Figure 6-19: Recorded Files Screen 26
Figure 6-20: Window Showing SnapShot Folders 27
Figure 6-21: Preferences Screen 27
Figure 6-22: Recording Schedule Screen 28
Figure 6-23: Add to Recording Schedule Screen 28
Figure 6-24: Stop Scheduled Recording Screen 29
Figure 6-25: View Video Screen 29
Figure 7-1: SoloLink Service 30
Figure 7-2: SoloLink Welcome Screen 30
Figure 7-3: SoloLink for Dynamic IP Address Screen 31
Figure 7-4: SoloLink for Convenience Screen 31
Figure 7-5: Check Connections Screen 32
Figure 7-6: Cameras Found Screen 32
Figure 7-7: Login Screen 33
Figure 7-8: SoloLink DDNS Screen 33
Figure 7-9: Confirm Active Internet Connection Screen 34
Figure 7-10: Welcome to the SoloLink DDNS Service Screen 34
Wireless-G Internet Video Camera
Figure 7-11: Sign Up Screen 35
Figure 7-12: Confirmation of New Settings Screen 36
Figure 7-13: Select a Location ID Screen 36
Figure 7-14: Confirm Your Location ID Screen 37
Figure 7-15: Payment Screen 37
Figure 7-16: Verification Screen 37
Figure 7-17: Create Links Screen 38
Figure 7-18: Successful Registration Screen 38
Figure 7-19: Account Confirmation of Camera Screen 39
Figure 7-20: Successful Setup Screen 39
Figure 7-21: Port Forwarding Information 40
Figure 7-22: Web-based Utility Welcome 40
Figure 7-23: Web Utility Login Screen 40
Figure 7-24: SoloLink DDNS Screen 41
Figure 7-25: Find Available Port Screen 41
Figure 8-1: Camera’s Default IP Address 42
Figure 8-2: Web-based Utility Welcome 42
Figure 8-3: Security Warning Screen 43
Figure 8-4: Web Utility Login Screen 43
Figure 8-5: Basic Screen 44
Figure 8-6: Confirmation Screen 45
Figure 8-7: WEP Key Settings Screen 45
Figure 8-8: Image Screen 46
Figure 8-9: Password Screen 47
Figure 8-10: Users Screen 48
Figure 8-11: Add/Modify User Screen 48
Figure 8-12: SoloLink DDNS Screen 49
Figure 8-13: New User Registration Screen 49
Figure 8-14: Password Request Screen 50
Figure 8-15: Manage Your SoloLink DDNS Account 50
Wireless-G Internet Video Camera
Figure 8-16: Device Removal Screen 50
Figure 8-17: Find Available Port Screen 51
Figure 8-18: Status Screen 52
Figure 8-19: Options Screen 53
Figure 8-20: Administrator Help 54
Figure 8-21: Upgrade Firmware Screen 55
Figure C-1: Upgrade Firmware Screen 64
1
Chapter 1: Introduction
Welcome
Wireless-G Internet Video Camera
Chapter 1: Introduction
Welcome
Thank you for choosing the Linksys Wireless-G Internet Video Camera. This Camera sends live video through the
Internet to a web browser anywhere in the world! This compact, self-contained unit lets you keep an eye on your
home, your kids, your workplace—whatever’s important to you.
How does the Camera do all of this? Unlike standard “web cams” that require an attached PC, the Internet Video
Camera contains its own web server, so it can connect directly to a network, either over Wireless-G (802.11b)
networking, or over 10/100 Ethernet cable. The advanced MPEG-4 video compression produces a high-quality,
high-framerate, up to 640 x 480 audio/video stream.
The Internet Video Camera’s unique form-factor and wireless connectivity allows you to mount it on a wall nearly
anywhere, or slip it into its included stand for desktop use. Once it’s connected to your home network, you can
“see what it sees” from any PC in the house, while the audio/video stream is secured from the outside world,
hidden behind your Router. If you want the video to be visible from outside your home network, you can open an
appropriate port on the Router, and then create password-protected accounts to manage access to the Camera,
or leave it wide open for the world to see. The SoloLink DDNS Service (trial sign-up included) lets you access your
Camera using an easy-to-remember “name”, even if your home Internet connection uses a dynamic IP address.
You can also turn on Security Mode, which tells the Camera to send you an e-mail message with a short video
attached to up to three e-mail addresses whenever it detects motion in its field of view. You can then log onto the
live video stream if the situation warrants. The included Viewer & Recorder utility lets you record the audio/video
stream to your local hard drive, “live” or on a predetermined schedule.
Use the instructions in this Guide to help you integrate the Camera into your network. These instructions should
be all you need to get the most out of the Wireless-G Internet Video Camera.
Ethernet: an IEEE standard network
protocol that specifies how data is
placed on and retrieved from a
common transmission medium.
802.11g: An IEEE wireless networking
standard that specifies a maximum
data transfer rate of 54Mbps, an
operating frequency of 2.4GHz, and
backward compatibility with 802.11b
devices.
2
Chapter 1: Introduction
What’s in this Guide?
Wireless-G Internet Video Camera
What’s in this Guide?
This user guide covers the steps for setting up and using the Wireless-G Internet Video Camera.
• Chapter 1: Introduction
This chapter describes the Camera’s applications and this User Guide.
• Chapter 2: Planning Your Wireless Network
This chapter discusses a few of the basics about wireless networking.
• Chapter 3: Getting to Know the Wireless-G Internet Video Camera
This chapter describes the physical features of the Camera.
• Chapter 4: Connecting the Wireless-G Internet Video Camera
This chapter instructs you on how to connect the Camera to your network before you run the Setup Wizard.
• Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera
This chapter instructs you on how to use the Setup Wizard for setup and configuration of the Camera, as well
as how to mount the Camera.
• Chapter 6: Installing and Using the Wireless-G Internet Video Camera Utility
This chapter explains how to install and use the Wireless-G Internet Video Camera Utility on your PC, so you
can view and record video.
• Chapter 7: Setting up the Linksys SoloLink™ DDNS Service
This chapter discusses the advantages of the SoloLink DDNS Service and walks you through the setup
procedure.
• Chapter 8: Using the Wireless-G Internet Video Camera Web-based Utility
This chapter describes the Web-based Utility and the features available, so you can use and alter advanced
configuration settings.
• Appendix A: Troubleshooting
This appendix describes some problems and solutions, as well as frequently asked questions, regarding
installation and use of the Camera.
• Appendix B: Wireless Security
This appendix discusses security issues regarding wireless networking and measures you can take to help
protect your wireless network.
3
Chapter 1: Introduction
What’s in this Guide?
Wireless-G Internet Video Camera
• Appendix C: Upgrading Firmware
This appendix explains how you can upgrade the Camera’s firmware.
• Appendix D: Windows Help
This appendix describes how you can use Windows Help for instructions about networking, such as installing
the TCP/IP protocol.
• Appendix E: Glossary
This appendix gives a brief glossary of terms frequently used in networking.
• Appendix F: Specifications
This appendix provides the technical specifications for the Camera.
• Appendix G: Warranty Information
This appendix supplies the warranty information for the Camera.
• Appendix H: Regulatory Information
This appendix supplies the regulatory information regarding the Camera.
• Appendix I: Contact Information
This appendix provides contact information for a variety of Linksys resources, including Technical Support.
4
Chapter 2: Planning Your Wireless Network
Introduction
Wireless-G Internet Video Camera
Chapter 2: Planning Your Wireless Network
Introduction
A wireless local area network (WLAN) is exactly like a regular local area network (LAN), except that each
computer in the WLAN uses a wireless device to connect to the network. Computers and other devices, such as
peripherals, in a WLAN share the same frequency channel and SSID, which is an identification name for wireless
devices.
Ad-Hoc and Infrastructure Modes
Unlike wired networks, wireless networks have two different modes in which they may be set up: infrastructure
and ad-hoc. An infrastructure configuration is a WLAN and wired LAN communicating to each other through an
access point. An ad-hoc configuration is wireless-equipped computers communicating directly with each other.
Choosing between these two modes depends on whether or not the wireless network needs to share data or
peripherals with a wired network or not.
If the computers on the wireless network need to be accessed by a wired network or need to share a peripheral,
such as a printer, with the wired network computers, the wireless network should be set up in infrastructure
mode. The basis of infrastructure mode centers around an access point, which serves as the main point of
communications in a wireless network. (A wireless router can also be used because a wireless router
incorporates the capabilities of an access point.) Access points transmit data to PCs equipped with wireless
network cards, which can roam within a certain radial range of the access point. Multiple access points can be
arranged to work in succession to extend the roaming range, and can be set up to communicate with your
Ethernet (wired) hardware as well.
If the wireless network is relatively small and needs to share resources only with the other computers on the
wireless network, then the ad-hoc mode can be used. Ad-hoc mode allows computers equipped with wireless
transmitters and receivers to communicate directly with each other, eliminating the need for an access point.
The drawback of this mode is that, in Ad-Hoc mode, wireless-equipped computers are not able to communicate
with computers on a wired network. And, of course, communication between the wireless-equipped computers
is limited by the distance and interference directly between them.
Network Layout
The Wireless-G Internet Video Camera is compatible with all 802.11b and 802.11g routers, such as model
numbers BEFW11S4 and WRT54G, as well as access points, including model numbers WAP11 and WAP54G. The
Infrastructure: configuration in which
a wireless network is bridged to a
wired network via an access point.
LAN (Local Area Network): the
computers and networking products
that make up the network in your home
or office.
Ad-hoc: a group of wireless devices
communicating directly to each other
(peer-to-peer) without the use of an
access point.
WLAN (Wireless Local Area
Network): A group of computers and
associated devices that communicate
with each other wirelessly.
5
Chapter 2: Planning Your Wireless Network
Network Layout
Wireless-G Internet Video Camera
Camera will also communicate with network adapters, such as the Wireless-B and Wireless-G Notebook Adapters
(model numbers WPC11 and WPC54G) for your laptop computers, Wireless-B and Wireless-G PCI Adapters (model
numbers WMP11 and WMP54G) for your desktop PCs, and Wireless-B and Wireless-G USB Adapters (model
numbers WUSB11 and WUSB54G) for your computers when you want to enjoy USB connectivity.
With these, and many other Linksys products, your networking options are limitless. Go to the Linksys website at
www.linksys.com for more information about products that work with the Wireless-G Internet Video Camera.
6
Chapter 3: Getting to Know the Wireless-G Internet Video Camera
Camera LCD Screen and Built-in Microphone
Wireless-G Internet Video Camera
Chapter 3: Getting to Know the Wireless-G Internet Video
Camera
Camera LCD Screen and Built-in Microphone
The Camera has a LCD screen that indicates the Camera’s current IP address and whether it is a fixed or dynamic
address. If the Camera uses a fixed IP address, then the screen will display the word “FIXED.” If the Camera uses
a dynamic IP address, then the screen will display the word “DHCP.”
The built-in microphone is located approximately one inch below the LCD screen, in the middle of the Camera’s
front panel. It has a range of approximately 9 feet (3 meters), depending on environmental conditions.
Camera LEDs
The Camera has four LEDs to let you know how the Camera is functioning.
READY Green. The READY LED lights up when the Camera is powered on. It flashes while the
Camera is initializing and is steadily lit when the Camera is ready for use.
ACT/LINK Green. The ACT/LINK LED flashes when there is activity.
ETHERNET Green. The ETHERNET LED lights up when there is a connection to a wired network. It flashes
when data is transmitted to or received from the wired network.
WIRELESS Green. The WIRELESS LED lights up when there is a connection to a wireless network. It
flashes when data is transmitted to or received from the wireless network.
Camera Head
The Camera head and its focus ring allow you to modify the aim and focus of the Camera.
To alter the Camera’s aim, swivel the Camera head.
To adjust the Camera’s focus, rotate the dark gray focus ring.
Figure 3-1: Camera LCD Screen and Built-in Microphone
Figure 3-2: Camera LEDs
Figure 3-3: Camera Head
Built-in
Microphone
7
Chapter 3: Getting to Know the Wireless-G Internet Video Camera
Camera Ports
Wireless-G Internet Video Camera
Camera Ports
The Camera features three ports and a Reset button on the bottom panel.
POWER The POWER port is where you will connect the power adapter.
MIC IN The MIC IN port is where you will connect the 2.5 mm input jack of your external microphone
(optional).
ETHERNET The ETHERNET port is where you will connect the Ethernet network cable.
RESET The RESET button is what you will press if you need to reset the Camera. Insert a paper clip
into the opening next to the Ethernet port. Then press the button and hold it in for five seconds. IMPORTANT: Resetting the Camera will erase
all of your settings, such as encryption
information, and replace them with the factory
defaults. Do not reset the Camera if you want
to retain these settings.
Figure 3-4: Camera Ports
8
Chapter 4: Connecting the Wireless-G Internet Video Camera for Setup
Overview
Wireless-G Internet Video Camera
Chapter 4: Connecting the Wireless-G Internet Video Camera
for Setup
Overview
Before you set up the Camera, connect it to a wired or wireless network. Proceed to the appropriate section for
your setup.
If you need to move the Camera from a wired network to a wireless network, or vice versa, go to this section,
“Moving the Camera to a Different Network.”
Connection to a Wired Network for Setup
1. Attach the antenna.
2. Connect the Ethernet network cable to your router, switch, or computer.
3. Connect the other end of the cable to the Ethernet port on the Camera. See Figure 4-1.
4. Connect the power adapter to the Power port on the Camera.
5. Plug the power adapter into an electrical outlet.
The Camera’s Ready LED flashes while the Camera is initializing. The Camera is ready for use when the Ready
and Ethernet LEDs are solidly lit.
Proceed to “Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera.”
Connection to a Wireless Ad-Hoc Network for Setup
1. Make sure your computer has the following wireless settings:
• SSID - linksys
• Network Mode - Ad-Hoc
• Channel - 6
• WEP - Disabled
2. Attach the antenna.
NOTE: You MUST connect the Camera to a PC,
router, or switch using the Ethernet network
cable BEFORE powering on the Camera.
Otherwise, the Camera will not function.
Figure 4-2: Connect the Power Adapter
Figure 4-1: Connect the Ethernet Network Cable
9
Chapter 4: Connecting the Wireless-G Internet Video Camera for Setup
Moving the Camera to a Different Network
Wireless-G Internet Video Camera
3. Connect the power adapter to the Power port on the Camera.
4. Plug the power adapter into an electrical outlet.
The Camera’s Ready LED flashes while the Camera is initializing. The Camera is ready for use when the Ready
and Wireless LEDs are solidly lit.
Proceed to “Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera.”
Moving the Camera to a Different Network
When you move the Camera from a wired network to a wireless network, or vice versa, you must power off the
Camera before connecting to the new network. Proceed to the appropriate instructions.
To move the Camera from a wired network to a wireless network, follow these instructions:
1. Unplug the power adapter from the Camera.
2. Unplug the Ethernet network cable from the Camera.
3. Re-connect the power adapter to the Power port on the Camera.
The Camera’s Ready LED flashes while the Camera is initializing. The Camera is ready for use when the Ready
and Wireless LEDs are solidly lit.
Proceed to “Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera.”
To move the Camera from a wireless network to a wired network, follow these instructions:
1. Unplug the power adapter from the Camera.
2. Connect the Ethernet network cable to your PC, router, or switch.
3. Connect the other end of the cable to the Ethernet port on the Camera.
4. Re-connect the power adapter to the Power port on the Camera.
The Camera’s Ready LED flashes while the Camera is initializing. The Camera is ready for use when the Ready
and LAN LEDs are solidly lit.
Proceed to “Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera.”
10
Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera
Setup Wizard
Wireless-G Internet Video Camera
Chapter 5: Setting up and Mounting the Wireless-G Internet
Video Camera
Setup Wizard
The Wireless-G Internet Video Camera Setup Wizard will guide you through the installation and configuration
procedure.
1. Insert the Setup CD-ROM into your CD-ROM drive. The Setup Wizard should run automatically, and the
Welcome screen should appear. If it does not, click the Start button and choose Run. In the field provided,
enter D:\wvc54g.exe (if “D” is the letter of your CD-ROM drive).
•Setup. Click the Setup button to begin the installation process.
•Install Viewer & Recorder Utility. Click this button to install the Camera’s Viewer & Recorder Utility on
your PC.
•Setup SoloLink DDNS Service. Click the Setup SoloLink DDNS Service button to configure and use
Linksys’s Dynamic Domain Name System (DDNS) service.
•User Guide. Click this button to open the PDF file of this User Guide.
•Exit. Click the Exit button to exit the Setup Wizard.
2. To install the Camera, click the Setup button on the Welcome screen.
3. When you see the screen shown in Figure 5-2, make sure the Camera is properly connected to either a wired
or wireless network. Then click the Next button to continue.
Figure 5-2: Connection for Setup Screen
Figure 5-1: Setup Wizard - Welcome Screen
11
Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera
Setup Wizard
Wireless-G Internet Video Camera
4. The screen shown in Figure 5-3 displays a list of Wireless-G Internet Video Cameras on your network, along
with the status information for the Camera whose name is highlighted. In the Selection box, click the name of
the Camera you are currently installing. Write down the IP address of the Camera, so you can use it to access
the Web-based Utility later. Click the Next button.
5. For security purposes, you will be asked to enter a name and password in order to have administrator access
to the Camera. In lowercase letters, enter admin in the Administrator Name and Administrator Password
fields (later you can change these through the Web-based Utility). Then click the OK button.
6. On the Basic Settings screen, you can alter the following settings:
•Camera Name. You can give the Camera a unique name. Memorable names are helpful, especially if you
are using multiple Cameras on the same network. It should have 15 characters or fewer.
•Description. You may enter additional information, such as location, in this field. It has a maximum length
of 32 characters.
•Time Zone. Select the time zone for the Camera’s location.
•Date. Enter today’s date in the fields provided.
•Time. Enter the current time in the fields provided.
When you have finished making your changes, click the Next button.
Figure 5-4: Login Screen
Figure 5-3: Cameras Found Screen
Figure 5-5: Basic Settings Screen
12
Chapter 5: Setting up and Mounting the Wireless-G Internet Video Camera
Setup Wizard
Wireless-G Internet Video Camera
7. If your network has a DHCP server, such as a router with DHCP enabled, click the Automatic Configuration-
DHCP radio button. If you need to assign a static IP address to the Camera, keep the default setting, Static IP
address.
Then click the Next button.
8. If you selected Automatic Configuration-DHCP in step 7, then proceed to step 9.
If you selected Static IP Address, then the IP Settings screen will appear. Enter an IP Address, Subnet Mask,
and Default Gateway appropriate for your network. You must specify an IP Address and Subnet Mask on this
screen. If you are unsure about the Default Gateway, it is better to leave this field blank. Then complete the
Primary DNS and/or Secondary DNS fields. You must enter at least one DNS address, which can be obtained
from your ISP. Click the Next button.
Figure 5-6: Network Settings Screen
Figure 5-7: IP Settings Screen