Pew study finds digital technologies help and challenge teachers

A survey conducted by the Pew Research Center found that the majority of Advanced Placement and National Writing Project teachers reported that digital technology in the classroom helps them teach middle and high school students in many ways. However, at the same time, the Internet, mobile phones, and social media also bring new challenges to education environments.

The survey also found that there are “striking differences in the role of technology in wealthier school districts compared with poorer school districts and that there are clear generational differences among teachers when it comes to their comfort with technology and its use in their classrooms.”

The teachers surveyed use a wide variety of digital tools in the learning process, including mobile phones, tablets, and e-book readers, most commonly to have students conduct research and access and submit assignments online.

To read more about the study, which was designed to explore teachers’ views of the ways today’s digital environment is shaping the research and writing habits of middle and high school students, as well as teachers’ own technology use and their efforts to incorporate new digital tools into their classrooms, click here.

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The difference between layer 2, 3, and 4 network switches

With the rapid development of computer networks over the last decade, high-end switching has become one of the most important functions of a network for moving data efficiently and quickly from one place to another.

Here’s how a network switch works: As data passes through the switch, it examines addressing information attached to each data packet. From this information, the switch determines the packet’s destination on the network. It then creates a virtual link to the destination and sends the packet there.

The efficiency and speed of a switch depends on its algorithms, its switching fabric, and its processor. Its complexity is determined by the layer at which the switch operates in the OSI (Open Systems Interconnection) Reference Model.

OSI is a layered network design framework that establishes a standard so that devices from different vendors work together. Network addresses are based on this OSI Model and are hierarchical. The more details that are included, the more specific the address becomes and the easier it is to find.

The Layer at which the switch operates is determined by how much addressing detail the switch reads as data passes through. Switches can also be considered MAC- or IP-level. A MAC-level switch operates in Layer 2 of the OSI Model and can also operate in a combination of Layers 2 and 3. IP-level switches operate in Layer 3, Layer 4, or a combination of the two.

Layer 2 Switches (The Data-Link Layer)
Layer 2 switches operate using the data link (MAC) layer addresses. Link-layer, hardware, or MAC-layer addresses identify individual devices. Most hardware devices are permanently assigned this number during the manufacturing process.

Switches operating at Layer 2 are very fast because they’re just sorting MAC addresses, but they do not look at the Layer 3 portion of the packet to learn anything more.

5 common digital video errors, their causes, and how to fix them

Today’s new digital video formats like HDMI and DVI provide uncompressed digital audio and video with a sharp, crystal-clear image quality. No more flickering and blurry pictures. However, even the best inventions have their limitations. Digital video signals require a huge amount of bandwidth to be transmitted properly. Using low-quality cabling or distribution equipment may lead to problems. Here are the five most common:

Problem #1: Black screen (no picture at all).
Possible cause: A. Bad cable or one that’s too long, causing either the video signals or EDID/HDCP control signals not to be transmitted properly. Make sure that you use good-quality, high-speed HDMI® cables—they don’t even have to be expensive ones—or try an HDMI extender. B. HDCP is unsupported. Does the display support HDCP? DVI displays usually don’t.

Problem #2: “Sparkles” in the picture.
Usually caused by: Too long or inferior HDMI cable. Use a video extender or change to active cables with equalization.

Problem #3: RGB color tint.
Usually caused by: A color encoding issue, a common problem when using a DVI display with an HDMI source. If you’re using a splitter or an extender between your source and the link, make sure it handles EDID. If possible, force the source (for instance, a Blu-ray player) to output HDMI video with RGB color encoding instead of Component (YCbCr) video encoding.

Problem #4: White noise, or just “snow,” for a picture.
Usually caused by: An HDCP issue. This is actually what the encrypted video looks like. It happens when your display (or any active component, like an extender or a splitter, used in the transmission) doesn’t support HDCP. The display, in turn, isn’t able to decrypt the video stream. Be sure to use equipment that supports HDCP.

Problem #5: Flickering, unstable, or blinking image.
Can be caused by: Electromagnetic or radio frequency interference (EMI/RFI), bad cable, or cable that’s too long. These all can cause issues with HDCP or the video signal, resulting in flickering or the video randomly disappearing then reappearing after a second. The solution: Use certified high-speed HDMI cables instead of standard HDMI cables, or if you need to transmit longer distances, try an extender or change to active cables with equalization.