Digital Signage How To: Networking Basics

-Scott Hofheins

The invention of the computer changed the way we see and interact with the world forever. Likewise, networking these computers together changed their very definition. It lets them work together like a single organism powering the internet, cloud applications, email, commerce, Youtube, Google...you name it.

The sign industry is no exception. We’ve gone from basic serial communication, to high speed 4G Cellular modems on full color digital billboard networks. Knowing how computers and networks function, even on a basic level is a worthwhile goal for anyone in the industry. My intention is to keep this as simple as possible, while still providing an accurate picture of how it all works.

Network Neighborhood
These days a computer can be anything: cellphones, laptops, desktops, signs, even cars! Networks are a collection of these devices organized into virtual neighborhoods in a virtual world. Just like us, these devices share information, maintain their ‘home’, and communicate with others across the globe. They have laws and standards that they must abide by, or the system can break. We call the most fundamental law TCP/IP and is the final word in whether or not devices can communicate with the others.

Addresses

Just like your house, these devices must have registered addresses according to TCP/IP rules. The address and other settings will look something like this:

• IP Address: 192.168.1.50 (your actual address)
• Subnet: 255.255.255.0 (the limitations of your address)
• Gateway: 192.168.1.1 (the address of the gateway to the internet)
• DNS #1: 192.168.1.1 (the address of your phone book)
• DNS #2: 8.8.8.8 (your backup phonebook)

Because everything is automated in this virtual world, devices cannot communicate over the network without an address. The mail man might show up, but if there is no number on a house he will run away confused, and usually drop your packet in the process. He doesn't even knock on the door.

Organization and Keeping the Peace

To avoid miscommunication and provide standard design structures for our private networks, TCP/IP tells us that our devices cannot communicate with another device unless it they both have addresses within a designated range. This is important for security and organization. You may not want the Hatfield area talking to the McCoys, it could get ugly. So you setup your Hatfield devices on a range of 192.168.1.50 thru 100, and your Mccoys on a range of 10.0.0.50 thru 10.0.0.100. This way, they still live in the same network without causing any issues.

Public and Private
Because this entire virtual world is governed by a strict numerical government, there is a limited number of addresses available. To minimize this problem, they have separated the world into Private Networks, and Public Networks. Private Networks have a smaller number of addresses they can use legally, at their leisure.  The Public Network has all the rest of the addresses, governed by the almighty ICANN. They keep a record of all public addresses and who they are assigned too. All communication between Private and Public networks rely on this record.

Private address numbers can be duplicated, as long as the duplicate numbers aren't in the same network. The mail labeled 1600 Pennsylvania in Springfield MO, will not go to the White House at 1600 Pennsylvania in Washington DC because they are in different "neighborhood". This is why it’s important that Public Addresses cannot be duplicated number for number, because they are in a single neighborhood we call “The Internet”.

Gated Communities

So how do we communicate with the public addresses like Google, or Facebook? Or across the internet, to email our grandma? Well it’s all about The Gateway. Every private network that wants to communicate to the outside world (or in some cases a larger internal network) must have a Gateway to these places. This is a device like a router, that will direct your devices communications back and forth correctly, over the internet. In other words, the gateway is the device that labels your communication for 1600 Penn in Springfield, MO...not Washington DC.

The Phone Book
Numbers are great, but not so easy to remember. You really don’t want to have to type in 74.125.227.224 to get to Google right? So we have DNS, or Domain Name Servers. These devices keep track of who’s name, is associated with what number. So when you type google.com, the DNS server looks up the number for that name, and sends you to the right place. Usually your Gateway (Router) will communicate directly with the DNS servers online, (this is why in a typical home network your Gateway address and DNS address are the same).

The Basics

It seems complicated at first, but when you really lay it out and look at the basics, it starts to make sense. Just remember these key points.

• Every device must have an IP address to access the network.
• To communicate with other devices, the addresses for each device must be in the same range.
• Devices access the internet through a Gateway. If you do not provide a Gateway address for the device, it can still communicate to your private network, but no further.
• The DNS server is your phone book, it looks up the numerical IP address associated with the name you typed into the browser and sends you to the right place.

-SH

I hope this post has been informative and helpful. As usual, I welcome ALL constructive comments. Please feel free to comment and add anything I’ve missed, or additional tips you may have regarding this topic. Please visit www.vantageled.com for many other resources, white papers, and of course: Great looking LED Signs!

**All posts/thoughts/writings are strictly the viewpoint of me and me alone and do not reflect nor speak for Vantage LED’s beliefs, attitudes, thoughts, etc. unless specifically stated.

Communication Methods for LED Signs / Electronic Message Centers: Wireless, Hard Wired, or Both?

LED Signs communicate information to the public, but how do you decide the best way to communicate to the sign? There are many ways to do this and each option has its own pros and cons, depending on your specific installation type.

There are (3) types of approaches to communication: wired, wireless, or both. Some locations have existing hard wiring to the sign site, others are more remote and using a cellular modem is the only realistic option.

WIRED (HARD LINE)   

  

In the past, before high speed networks were common, LED signs were usually hardwired using a phone modem or serial cable (RS485 or RS232). These options were fine back then, because the signs were less sophisticated and the actual data sent to the sign was minimal. As LED sign technology expanded, larger file sizes were required. These options became less common and were replaced by standard Ethernet network cable or Fiber Optics. The older options are still used in special situations like factory production floors where they have a large serial network with simple machine code, but for the commercial market Ethernet and Fiber have become the standard wired solution.
 
 
Ethernet TCP/IP  (Cat5/6 Cable - RJ45 Ends)

 
This is a common option for wall mounted signs, or street signs that are closer to the building or network drop, where the cable run is less than 300 Ft. Most LED sign manufacturers offer this connectivity imbedded into their system without any special adapters. Signs that require separate “Ethernet Adapters” may be using older Serial based controllers.

• Maximum run is 300ft without a network switch in the middle to boost the signal.
• Less fragile than Fiber Optics. Harder to damage.
• Ethernet networks are very common, and the cable is inexpensive.

Fiber Optic Cable

 
Although somewhat rare in commercial LED sign installation, Fiber is still commonly used in the military. Data is sent using light signals across refined glass strands that make up the fiber optic cable. An “Fiber Optic to Ethernet” converter is usually required on both sides of the system: one placed at the sign, and the other at the building where it connects to the main Ethernet network.

• Long distance capability near 40 miles with Single-Mode (more expensive), and 10 miles using Multi-Mode (less expensive).
• Fragile, and can be expensive to run and repair if damaged.

WIRELESS

  
You can get Wireless Radios that connect to serial networks, cellular networks, and standard Ethernet TCP/IP networks. Many frequency standards can be used, but the most common ranges are 900 Mhz, 2.4 Ghz, 5 Ghz and Cellular. Wireless radios have become the standard option for most manufacturers because they allow for a broad range of installation types, and can save time and money by not having to run a hard line in the ground.

Wireless is best when you have an LED sign that will be within 100-200 yards of the transmission point with clear “Line of Site” (no buildings or metal walls between the radios). The most common configuration  is (1) wireless radio installed at the sign, and (1) at the building. You connect the building radio to your network, or computer directly and the radios function as a long wireless “cable” connecting you to the sign. Other configurations can be used depending on the installation like Point to Multipoint, WiFi Access Point, and others.  

Common Frequency Types:

900 Mhz (slower data rate, longer distance): These were much more common in the past, when serial networks abundant. However, there are products out there that will use a multi channel 900 Mhz signal with a standard ethernet network to boost the data rate. These radios are best used for installation with special needs like distance or if the signal needs to go through structures between the sign and the transmission point.

2.4 Ghz (standard WiFi frequency): These radios are the most common, and have a good balance of distance and data rate. 2.4 Ghz is the most used frequency in the USA for home and commercial WiFi networks. This poses a slightly larger security risk for your sign, if the radios are not secured properly. (Deacon’s post on LED sign security)

5 Ghz (higher data rate, more secure): This frequency is less common than 2.4 Ghz, making it a bit more secure because most hackers are not looking for signals in the 5 Ghz range. You also avoid possible interference from other 2.4 Ghz devices in the area. Many manufacturers are leaning toward this option as the default choice for LED signs.

Cellular Modem

Another wireless option is a Cellular Modem. These are gaining popularity, but are less commonly used for LED signs. They provide access to the sign over the same data network as your smart phone (3g, 4g, LTE, etc..). Without getting too technical, the system works like this:

After purchasing a “Data Only” monthly plan through a wireless carrier supported by the Cell Modem (ATT, Verizon, T-Mobile, Sprint),  the wireless provider will then provide an external internet IP address for the Cell Modem to use. The Cell Modem is installed and connected to the sign (likely using a secured router). You can then send messages to the sign over the internet by using the unique IP address previously provided.

This option is best used for signs that are controlled off-site, in remote locations, or outdoor digital billboards.

WIRELESS AND HARD LINE

I’ve been on installations who utilize both options as a fail-safe measure when the sign is providing mission critical data. This is more common in a military setting, but I’ve seen schools and other government organizations use this approach. For the average user, I believe it’s overkill, but if you do decide to take this route make sure you communicate this to the manufacturer. Some manufacturers will need to put an extra “Network Switch” inside the sign, and this can be an extra fail point. Others will have multiple network ports built into their sign control unit, a much better solution in my opinion.


Conclusion

The bottom line is, make sure you work with the manufacturer or LED sign dealer to get the best solution for your installation. Not being able to communicate with your brand new sign because the communication method is in-correct can really ruin the excitement of the moment. If your manufacturer doesn’t pre-program street ready messages on the sign, you may be stuck with “Sign Test 3” scrolling across the sign until the communication is fixed.

Make sure your manufacturer secures the wireless devices prior to shipment, and allows you to configure them with your own security measures if needed. Communication to your sign is a fundamental necessity, make sure you get the best solution and equipment from your manufacturer.


-Scott Hofheins



I hope this post has been informative and helpful. As usual, I welcome ALL constructive comments. Please feel free to comment and add anything I’ve missed, or additional tips you may have regarding this topic. Please visit www.vantageled.com for many other resources, white papers, and of course: Great looking LED Signs!

**All posts/thoughts/writings are strictly the viewpoint of me and me alone and do not reflect nor speak for Vantage LED’s beliefs, attitudes, thoughts, etc. unless specifically stated.