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For the past several weeks we’ve looked at blinky LEDs, 555 timers, and resistors. This week it’s time to put it all together into an application. A YouTube subscriber suggested the project as follows: How would you go about having an led blink twice, then a different one blink twice, then back to the original …
As we learned from the last video, resistors are helpful when you want to limit current. They are also helpful if you want to divide a voltage level, but in order to do any of this, it’s important to understand all about a resistor’s power rating. In this video you’ll learn how much power a …
Power Dissipation and How to Avoid Destroying a Resistor Read More »
In this weeks video we’ll take a look at how to use an LED. There are tons of LED related projects out there but what if you want to integrate LEDs in your own project? When your finished with this video you’ll be able to pick the appropriate type of LED for your project and …
The 555 timer has many uses and in this video we’ll explore two different ways to utilize the output. First we’ll see how the the timer can be used to source and sink current and secondly we’ll look at a way to use the timer as a control mechanism for another circuit. If you missed …
I am slowly in the process of developing another class, but this time I want to go about it a different way. I’m going to be letting everyone else in on the process. The coming class will include a lot of projects, so during the development of different modules, I want to present some of …
In the course of my normal job, it’s surprising how often field expedient solutions are used to solve a problem. However, those field expedient solutions are impossible unless you understand the underlying principles involved. In this video I’ll look at Ethernet infrastructure, discuss how it works, and build a passive network tap.
When I was developing the VoIP Fundamentals course, I wanted a demonstration to illustrate the simplicity of the public switched telephone network. After combing through the internet, I came across this ingenious little project. With just a 9V battery, a resistor, a telephone cord, and a couple of phones you can create a simple little intercom …
9 Volt, Battery Powered, Telephone Intercom System Read More »
Auto Answer is a feature in many VoIP phones that allows the phone to go off-hook the very instant a call is received by the instrument. In this video we’ll look at how this feature is setup and talk about the security vulnerabilities. NIST Report: Link Video Conferencing Auto Answer: Link 1 Link 2 Link 3
Sometime when performing a packet capture, you may come across some VoIP conversations. If the initial call setup is not in this capture, subsequent voice packets will be labeled in such a way that it makes it difficult to decode the VoIP conversation. What follows is a tutorial to get around this problem.
At one time I had the misconception that you had to have an IP PBX to use a VoIP phone, but it’s simply not true. In this video I’ll show you how to dial another VoIP phone without routing through the PBX or SIP Proxy. Linphone: http://www.linphone.org Grandstream phones for under $50: http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=grandstream&_udhi=50
