220-1101 CompTIA A+ Certification Exam: Core 1 Free Practice Exam Questions (2025 Updated)

The user should check the display settings on the computer and set them to extend/duplicate. This will allow the computer to send the video signal to both the laptop screen and the projector. If the display settings are set to only show on one screen, then the projector may not detect any source. According to the CompTIA Core1 objectives, one of the common display issues is no image on screen. A troubleshooting guide for projectors also suggests checking the display settings as a possible solution for no source found error.

Application virtualization is a technique that allows an application to run on a computer without being installed or affecting other applications on the system. Application virtualization creates a virtual environment for the application that isolates it from the underlying operating system and hardware. This way, the technician can verify the application deployment will not affect other legacy applications on the end users’ computers.

The correct answer is D. 5,400rpm HDD.

A 5,400rpm HDD (Hard Disk Drive) is a type of storage device that uses spinning magnetic disks to store data. A 5,400rpm HDD is the least expensive per gigabyte among the options given, as it has a lower rotational speed and performance than other types of HDDs or SSDs (Solid State Drives). A 5,400rpm HDD is suitable for archiving a large number of photos that are not accessed frequently, as it can offer high capacity and reliability at a low cost.

the average cost per gigabyte of a 5,400rpm HDD is around $0.02 to $0.0312, while the average cost per gigabyte of the other options are:

NVMe SSD: $0.10 to $0.1534

SCSI RAID: $0.20 to $0.305

15,000rpm SAS: $0.30 to $0.40

Therefore, a 5,400rpm HDD is the cheapest option among the four.

One of the possible causes of the error message “No Source Found” is that the projector is not receiving any signal from the connected device, such as a laptop1. This could be due to an incorrect input source selected on the projector or an improper display setting on the laptop. Therefore, the first actions that the technician should take are to verify the projector settings and make sure the correct input is selected, and to check the laptop display settings and set them to extend/duplicate23.

The correct answer is C. The battery.

The battery is the component that stores and provides electrical power to the phone. The battery can degrade over time and lose its capacity to hold a full charge. This can cause the phone to stop charging at a certain percentage and run out of power faster. To resolve this issue, the battery should be replaced with a new one that is compatible with the phone model and manufacturer.

To replace the battery, the customer may need to follow different steps depending on the type of phone and battery. Some phones have removable batteries that can be easily accessed by opening the back cover of the phone and sliding out the old battery. Other phones have non-removable batteries that are sealed inside the phone and require special tools and skills to open the phone and disconnect the old battery. In this case, the customer may need to contact the phone manufacturer or a professional service center for assistance.

The most likely cause of the issue is C. Physical cabling issues.

Physical cabling issues can affect the quality and stability of the display signal. If the cable is loose, damaged, or bent, it may cause intermittent connection, interference, or signal loss. This can result in slow, distorted, discolored, or blank display.

To troubleshoot physical cabling issues, the user should check the following steps:

•Make sure the cable is firmly connected to both the display and the video adapter.

•Inspect the cable for any signs of damage, such as cuts, frays, kinks, or exposed wires.

•Check the cable connectors for any bent or broken pins.

•Try a different cable or a different port on the display or the video adapter.

•If possible, test the display with another device or test another display with the same device.

The other options are less likely to cause the issue, because:

•Incorrect data source may result in no display or an error message, but not slow or distorted display.

•Incorrect resolution settings may cause stretched, blurry, or cropped display, but not discolored or blank display.

•Incorrect refresh rate may cause flickering or tearing display, but not slow or distorted display.

•Display burn-in may cause permanent image retention or ghosting on the display, but not intermittent or blank display.

For more information and tips on how to fix common display problems, you can visit these links:

•How to Troubleshoot Display or Video Issues on a Dell Monitor

•Display Troubleshooting - iFixit

•How to Fix the Most Common Problems With LCD Monitors

The correct answer is D. PAN.

A PAN, or Personal Area Network, is a type of network that connects devices within a short range, usually less than 10 meters, and is used by an individual. A PAN can be wireless or wired, and it can enable data transmission between devices without requiring an internet connection. A PAN can also be connected to a LAN or a higher level network, where one device acts as a gateway.

A Bluetooth hotspot is an example of a wireless PAN, where a device such as a smartphone or a laptop can create a network with other Bluetooth-enabled devices nearby. A Bluetooth hotspot can allow devices to share files, access the internet, or use peripherals such as printers or speakers.

A SAN, or Storage Area Network, is a type of network that connects storage devices such as hard disks, tape drives, or optical drives to servers. A SAN provides high-speed data transfer and access to large amounts of data. A SAN is usually used in data centers or enterprises that need to store and manage huge volumes of data.

A WAN, or Wide Area Network, is a type of network that connects devices over a large geographical area, such as across cities, countries, or continents. A WAN can use different technologies and media to transmit data, such as fiber-optic cables, satellite links, or radio waves. A WAN can also consist of multiple LANs or other types of networks. The internet is the largest example of a WAN.

A LAN, or Local Area Network, is a type of network that connects devices within a limited area, such as within a building or a campus. A LAN can use wired or wireless technologies to transmit data, such as Ethernet cables, Wi-Fi routers, or switches. A LAN can enable devices to share resources, such as printers, scanners, or files.

For more information about the types of networks and their differences, you can refer to the following web search results: 11 Types of Networks: Understanding the Differences, Types of Computer Networks, Types of network - Introduction to networks.

A PSU (power supply unit) is a component that converts the AC power from the wall outlet into DC power that the PC components can use. A faulty or failing PSU can cause random system crashes, as well as other problems such as noise, overheating, or no power at all. A PSU can fail due to various reasons, such as age, dust, power surges, or poor quality.

To troubleshoot a PSU, the technician can use a multimeter to measure the voltage output of the PSU connectors. The voltage should be within the acceptable range of the specifications. For example, the 12V rail should be between 11.4V and 12.6V. If the voltage is too low or too high, the PSU is likely defective and needs to be replaced.

Alternatively, the technician can try swapping the PSU with a known good one and see if the system crashes persist. If the system works fine with a different PSU, then the original PSU is the problem and should be replaced.

The other options are not likely to fix the random system crashes. Testing the fan speed may help to diagnose overheating issues, but it is not related to the PSU. Disabling the USB ports may help to eliminate potential conflicts with USB devices, but it is not related to the PSU. Decreasing the RAM timings may help to improve performance and stability, but it is not related to the PSU.

A thermal receipt printer uses heat to print on thermal paper, which has a special coating that reacts to heat and produces black marks. If the paper roll is inserted in the wrong orientation, the printer will not be able to print anything on the paper. Therefore, the first thing the technician should do is to check if the paper roll is loaded correctly, with the paper feeding under, not over. This is a common and easy mistake to fix, and it does not require any software or hardware changes.

References

•Troubleshooting Your Thermal Printer Problems - Thermal POS Receipt Printer Tips & Tricks, paragraph 2

•POS Thermal Receipt Printer Troubleshoot - Not Printing Evenly, video at 0:15

•Receipt Printer Troubleshooting – Shopfront, bullet point 2

When troubleshooting a thermal receipt printer that fails to print, the CompTIA A+ Core 1 Study Guide advocates starting with the simplest, most common, and least invasive steps before escalating to more complex solutions. Thermal printers rely on heat-sensitive paper, and a frequent issue is incorrect paper orientation—thermal paper has a coated side that must face the printhead to produce an image. If the paper roll is installed upside down, the printer won’t print, as the heat from the thermal head won’t interact with the correct side of the paper. This is a quick fix that doesn’t require tools or software changes, aligning with CompTIA’s troubleshooting methodology (Objective 5.6: "Given a scenario, troubleshoot and resolve printer issues").

D. Flip the paper roll orientation: Checking and correcting the paper orientation is a basic, immediate step that addresses a common thermal printer issue. It’s non-disruptive and aligns with initial troubleshooting principles.

A. Update the printer driver: Driver issues could prevent printing, but this assumes a software problem without evidence and isn’t the first step when hardware basics haven’t been checked.

B. Replace the thermal printhead: A failed printhead could cause non-printing, but replacing hardware is a later step after ruling out simpler causes, as it’s costly and invasive.

C. Make sure the thermal head is heating up: Verifying the printhead’s functionality is a valid diagnostic step, but it requires tools (e.g., checking heat output) and assumes a hardware failure, making it less immediate than checking paper orientation.

The study guide emphasizes starting with physical checks—like paper installation—before moving to software or hardware diagnostics, making flipping the paper roll the most logical first action.

Exact Extracts from the Study Guide:

From The Official CompTIA A+ Core 1 Study Guide (220-1101):

Section 3.7, Printer Consumables:

"Thermal Printers: Thermal printers use heat to create an image on specially coated paper… The paper must be loaded correctly, with the coated side facing the thermal printhead, or no image will be produced. If the printer is not printing, check the paper orientation first."

Implication: Incorrect paper orientation is a primary cause of printing failure in thermal printers.

Section 5.6, Troubleshooting Printer Issues:

"Printer will not print—Verify that the printer is powered on and online… Check that the paper is loaded correctly (for thermal printers, ensure the coated side faces the printhead). Next, check for paper jams, then verify connectivity and driver settings."

"Troubleshooting methodology: Identify the problem… Test the simplest solutions first (e.g., paper loading, power, cables) before escalating to software or hardware replacement."

These excerpts confirm that checking paper orientation is the initial step for thermal printer issues, as it’s a frequent user error and easily corrected.

Additional Reasoning:

Thermal Printer Mechanics: Thermal receipt printers don’t use ink or toner; they heat the paper directly. If the non-coated side faces the printhead, no output occurs, making orientation a top troubleshooting priority.

Symptom Specificity: The printer “will not print” suggests no output at all, not faded or partial printing (which might point to a printhead or driver issue). Paper orientation fits this symptom perfectly.

CompTIA Approach: The methodology prioritizes quick, low-cost checks (paper, power, connections) over software updates or hardware swaps, especially in a SOHO or retail environment where receipt printers are common.

Other Options:

Driver Update (A): Relevant if the printer is online but not responding to print jobs, not the first step without connectivity clues.

Replace Printhead (B): Premature without testing the existing head’s functionality.

Check Heating (C): Useful but requires diagnostic effort (e.g., test page or thermal test), making it a follow-up step.

The most likely answer is C. The pen batteries need recharging.

An active touch pen is a stylus that uses a battery to power features such as pressure sensitivity, buttons, or Bluetooth connectivity. If the pen batteries are low or depleted, the pen may stop working or become inaccurate1. To fix this issue, you should recharge the pen batteries using the provided charger or cable, or replace them with new ones if they are not rechargeable1.

The other options are less likely to cause the issue. A scratched tablet screen may affect the touch sensitivity, but it should not affect the pen functionality. The pen software may need updating to improve performance or compatibility, but it should not stop the pen from working altogether. Software updates may disable the pen if they change the settings or drivers, but this can be fixed by re-enabling the pen or reinstalling the drivers2.

According to the CompTIA troubleshooting methodology, the next step after establishing a theory of probable cause is to test the theory to determine the cause. However, before testing the theory, the technician may need to conduct some research based on the symptoms and the possible cause. This may involve consulting online resources, manuals, documentation, or colleagues to find out more information about the power supply and how to test it. Research can help the technician confirm or eliminate the theory and avoid unnecessary actions or damage.

Answer A is incorrect because inquiring about environmental or infrastructure changes is part of identifying the problem, which is the first step of the troubleshooting methodology. The technician should have already done this before establishing a theory of probable cause.

Answer C is incorrect because establishing a plan of action to resolve the problem and implement the solution is the fourth step of the troubleshooting methodology. The technician should not jump to this step without testing the theory and verifying the cause.

Answer D is incorrect because documenting the findings, actions, and outcomes is the last step of the troubleshooting methodology. The technician should not do this until the problem is resolved and verified.

The first step in troubleshooting a computer that does not turn on when the power button is pressed is to check if there is any power going to the computer. The technician should reseat or reconnect the power cable to ensure it is firmly attached to both ends, and confirm that the outlet or power strip is providing energy by using a multimeter or another device. This can eliminate any issues with loose or faulty connections or power sources, and help isolate the problem further. Reference: https://partners.comptia.org/docs/default-source/resources/a-core-series-combined-content-guide (page 28)

One of the benefits of virtualization is that it allows you to create and manage multiple virtual machines (VMs) on a single physical computer. This can be used to enhance security by centralizing all user desktops on a server, rather than storing them on individual user machines. This way, the user desktops can be isolated from each other and from the host machine, preventing malware infections, data breaches, and unauthorized access. Additionally, the user desktops can be easily backed up, restored, updated, and monitored by the administrator, reducing the risk of data loss and downtime.

This type of virtualization is called desktop virtualization, and it separates the desktop environment from the physical hardware the user interacts with1. The user can access their virtual desktop from any device, such as a laptop, tablet, or smartphone, using a remote display protocol. The user experience is similar to using a local desktop, but with improved security and manageability.

DNS stands for Domain Name System, which is a network service that translates hostnames to IP addresses. Hostnames are human-readable names that identify devices or services on the Internet, such as www.google.com or mail.yahoo.com. IP addresses are numerical identifiers that specify the location of devices or services on the Internet, such as 172.217.14.206 or 98.137.11.163. DNS allows users to access websites or services by using hostnames instead of IP addresses, which are easier to remember and type. DNS also allows hostnames to change their IP addresses without affecting the users, which can improve performance and security.

The correct answer is C. PoE switch.

A PoE switch is a network device that can provide both data and power to other devices over an Ethernet cable. PoE stands for Power over Ethernet, which is a technology that allows electrical power to be transmitted along with data on twisted pair Ethernet cabling. This eliminates the need for separate power supplies or AC adapters at the users’ desks, as the VoIP devices can receive power from the PoE switch12.

A firewall is a network device that monitors and controls incoming and outgoing network traffic based on predefined security rules. It does not provide power to other devices1.

A power injector is a device that adds electrical power to an Ethernet cable for a single device. It is not suitable for a large number of devices, as it would require one power injector per device1.

A router is a network device that connects multiple networks and forwards data packets between them. It does not provide power to other devices1.

Port flapping, also known as link flapping, is a situation in which a physical interface on the switch continually goes up and down, causing intermittent connectivity for the devices connected to that port12. Port flapping can be caused by various factors, such as faulty or incompatible cables, hardware issues, configuration errors, or other network problems123.

The network logs show that interface 0/1 on the switch changes its status from up to down and vice versa several times within a short period of time. This indicates that the port is flapping and affecting the network connectivity. The log also shows that the switch was elected as the root bridge, which means that it is the central point of a spanning tree protocol (STP) network. STP is a protocol that prevents loops in a network by blocking some ports and creating a tree-like topology. Port flapping can cause STP to recalculate the topology and change the status of the ports, which can further disrupt the network performance2.

To troubleshoot port flapping, the technician should check the physical and hardware aspects of the device, such as cables, SFPs, gigabit interface converters, and power supplies. The technician should also check the configuration settings of the port, such as auto-negotiation, duplex mode, speed, power-saving features, and smartport. The technician should also check for other network issues that may cause port flapping, such as link synchronization and spanning tree issues123.

The correct answers are C. Pickup roller and D. Separation pad.

A pickup roller is a rubber wheel that grabs the paper from the paper tray and feeds it into the printer. A separation pad is a small piece of cork or rubber that prevents more than one sheet of paper from being fed at a time. If the pickup roller or the separation pad is worn out, dirty, or damaged, it can cause the printer to pull multiple sheets of paper instead of a single sheet. This can lead to paper jams, misprints, or wasted paper.

To resolve this issue, a technician should investigate the condition of the pickup roller and the separation pad and replace them if necessary. The technician should also clean the paper tray and make sure the paper is loaded correctly and not stuck together.

A toner cartridge is a component that contains the toner powder used to create the printout on a laser printer. A tractor feed is a mechanism that uses sprockets to move continuous paper through a dot matrix printer. A duplexer is a device that allows a printer to print on both sides of the paper automatically. A fuser is a part of a laser printer that melts the toner onto the paper using heat and pressure. None of these components are related to the issue of pulling multiple sheets of paper from the paper tray.

three beeps and a black screen indicate a memory error of some sort123. This means that the RAM may not be properly installed or connected to the motherboard. Reseating the RAM means removing each stick and re-inserting it, making sure it clicks into place. This can sometimes solve the problem by ensuring a good contact between the RAM and the motherboard.

Replacing the power supply, reattaching the hard drive, or flashing the BIOS are unlikely to fix this issue, since they are not related to the memory error. The power supply provides power to the whole system, the hard drive stores data, and the BIOS is the firmware that controls the boot process. None of these components would cause three beeps and a black screen if they were faulty.

The next troubleshooting step that the technician should attempt is to restart the smartphone. Restarting the smartphone can help resolve many common issues, such as battery drain, network utilization, app crashes, or performance slowdowns. Restarting the smartphone can do the following:

Clear the memory and cache of the smartphone, which can free up space and speed up the device.

Close any background apps or processes that may be consuming battery or network resources, such as syncing, updating, or streaming.

Reset the network settings and connections of the smartphone, which can improve the signal strength and quality.

Refresh the operating system and the user interface of the smartphone, which can fix any glitches or errors.

To restart the smartphone, the user can follow these steps:

Press and hold the power button of the smartphone until a menu appears on the screen.

Tap the option that says Restart, Reboot, or Power off and on.

Wait for the smartphone to turn off and then turn on again.

Enter the PIN, password, or pattern to unlock the smartphone.

Check the battery level and the network utilization of the smartphone.

If restarting the smartphone does not solve the problem, the technician may need to try other troubleshooting steps, such as updating the mobile OS, disabling Bluetooth, or connecting the smartphone to a Wi-Fi network. However, restarting the smartphone is usually the first and simplest step to try.

The disk failure notice during startup indicates that one or more disks in the RAID array have failed. The machine still seems to startup into Windows but at a much slower speed because the RAID 5 configuration can tolerate one disk failure and still operate, but with reduced performance and reliability. The technician most likely needs to rebuild the RAID, which means replacing the failed disk(s) and restoring the data from the parity information. Reinstalling the HDD drivers will not fix the disk failure. Replacing the failed drivers is not a valid option, as drivers are software, not hardware. Restarting the system will not fix the disk failure either. References: https://www.comptia.org/blog/what-is-raid-0-1-5-6-10

The correct answer is D. Sandboxing.

Sandboxing is a security technique that isolates email attachments in a safe place until the attachments can be scanned for malware. A sandbox is a virtual environment that mimics the operating system and applications of the user, but prevents any changes or damage to the actual system. A sandbox can also monitor the behavior and activity of the attachments and detect any malicious code or actions12.

An approve listing is a security technique that allows only trusted or authorized email senders or domains to be received by the user. An approve listing can help reduce spam and phishing emails, but it does not scan or isolate email attachments for malware3.

A screened subnet is a security technique that creates a buffer zone between the internal network and the internet. A screened subnet uses firewalls and routers to filter and control the traffic that enters and exits the network. A screened subnet can help protect the network from external attacks, but it does not scan or isolate email attachments for malware.

Cross-platform virtualization is a technology that allows running multiple operating systems and applications on the same physical machine. Cross-platform virtualization can help improve efficiency, flexibility, and compatibility, but it does not scan or isolate email attachments for malware.

The technician should replace the patch cable that connects the desktop to the network switch or outlet. The patch cable may be damaged or incompatible with the upgraded network infrastructure, which can cause slow network speeds. According to the CompTIA Core1 objectives, one of the common symptoms of a bad cable is slow transfer speeds. A research paper on network performance also states that cable quality and length can affect network speed.

The clicking sound is the sound of a damaged disk in the HDD

A clicking sound from a hard disk drive typically indicates a mechanical failure, such as the read/write head hitting a physical obstruction or a problem with the disk motor. This can cause the drive to fail to initialize or not be recognized by the system during booting.

When a user hears one beep on rebooting a machine, and then an error message is displayed, it could indicate that there is a problem with the RAM module or the boot order. The beep sound indicates that the POST process was successful, and the error message indicates that the boot process was unsuccessful. The boot order determines the sequence in which the computer looks for bootable devices. References: CompTIA A+ Certification All-in-One Exam Guide, Tenth Edition by Mike Meyers (Page 693)

Three beeps indicate a "base memory read/write test error". Check out "beep codes" for more information.

https://en.wikipedia.org/wiki/Power-on_self-test#POST_beep_codes_on_CompTIA_A.2B_certification_exam

Reseating the RAM is the best course of action to remediate the issue of three consecutive beeps during boot, as it may indicate a RAM failure or loose connection. By reseating the RAM, the technician can ensure that the connection is secure and the computer should boot normally. References: CompTIA A+ Certification Exam Objectives 1001, 1.9

The tool that the technician should use to see all drives is Diskmgmt. Diskmgmt is a Windows utility that allows you to manage disk drives and partitions on your computer. It can be used to view all drives, including USB drives, that are connected to the computer12.

After the issue has been identified and the backup of the system has been made, the next step is to establish a theory of probable cause. This involves researching the issue to determine the root cause of the problem. This can involve researching internally (e.g. referring to the system logs) or externally (e.g. searching online). Once the probable cause has been identified, the technician can then move on to the next step of designing a plan of action to resolve the issue and implementing the solution.

Private cloud environments are designed for use by a single organization and offer the greatest control over security and access to data. They are typically used for sensitive or confidential data, such as health and criminal justice records. Public cloud environments are shared by multiple organizations and offer less control over security and access to data. Hybrid cloud environments combine public and private clouds, while community clouds are shared by multiple organizations with similar needs. References: CompTIA A+ Certification Exam: Core 1 - Page 234

https://techlibrary.hpe.com/docs/iss/proliant-gen10-uefi/s_enabling_VT-d.html

Enabling VT-d (Virtualization Technology for Directed I/O) in the server's BIOS settings is required for the hypervisor to run properly. References: CompTIA A+ Certification Exam Guide, Ninth Edition, Chapter 11

The component that should be upgraded first is the RAM. When multiple applications are being utilized, the system’s response time slows down drastically. This is because the computer is running out of memory. Upgrading the RAM will allow the computer to store more data in memory, which will improve performance when multiple applications are being used123.

The digitizer is the component that enables input on a mobile device's touch screen. It is a transparent layer that sits over the screen and detects the location of touch inputs. OLED (Organic Light Emitting Diode) is a type of display technology. Inverter is a component used in older LCD displays to provide power to the backlight. CMOS (Complementary Metal-Oxide-Semiconductor) sensor is a type of image sensor used in digital cameras and smartphones to capture images. References: CompTIA A+ Certification Exam: Core 1 - Page 177

The symptoms suggest that the charging cable falls out of the phone, indicating that the charge port may contain foreign objects such as lint, which can interfere with the connection between the charging cable and the phone.

NFC (Near Field Communication) is a technology used for short-range wireless communication between devices, typically used for contactless payments and authentication. In this scenario, the 13.56MHz frequency short band was implemented, and users can authenticate using their mobile devices, which requires NFC to be enabled on the device. References: CompTIA A+ Certification Exam Objectives 220-1001 - Mobile device network and device synchronization - 4.4

Based on the information provided in the scenario, the most likely cause of the issue is that the user’s internet connection is down (option A). This would explain why the user is unable to access any of the organization’s servers or network items and why web pages are not functioning. However, since the user can still access local file folders and other local machines, it suggests that their local network is still functioning.

The user can access local file folders and other local machines but none of the organization's servers or network items, indicating that the issue is with the user's internet connection, not with the user's domain account, switch, or IP address.

When a user receives a notification indicating that there is limited or no connectivity, it means that their device is unable to establish a connection to the network. In this scenario, the user can access local file folders and other local machines but is unable to access any of the organization’s servers or network items and web pages are not functioning. This suggests that the issue is with the user’s internet connection.

An internet connection allows a device to communicate with other devices and servers outside of its local network. If the internet connection is down or not functioning properly, the device will be unable to access any resources outside of its local network. This would explain why the user in this scenario can still access local resources but is unable to access any of the organization’s servers or network items.

solution as

The most likely action that would resolve the issue is to clean the keyboard. Sometimes dust, hair, and other debris can affect keyboard functionality. The technician can try to clean the keyboard as much as possible, which may be enough to get the keyboard back in working order

To fix a Cat 5 cable issue where the cable fails when it is moved around, the technician would need to use an RJ45 connector (option E) and a crimper (option F). The technician can use the crimper to attach a new RJ45 connector to the end of the cable, which should resolve the issue.

An RJ45 connector (option E) is a type of connector commonly used for Ethernet networking. It is an 8-position, 8-contact (8P8C) modular plug and jack that is used to terminate Cat 5 and other types of twisted pair cables. A crimper (option F) is a tool used to attach connectors to the ends of cables. In this case, the technician would use the crimper to attach a new RJ45 connector to the end of the Cat 5 cable.

When a cable fails when it is moved around, it often indicates that there is a problem with the connector at the end of the cable. By attaching a new RJ45 connector using a crimper, the technician can ensure that the cable has a secure and reliable connection.