This is a telephone line over voltage protector. This is basen on a design I did originally around 1995. Has been available for almost 30 years. That white thing is a deal gas discharge tube over-voltage protector that dissipates most of the over-voltage surge. It is followed with two other layers of protection (VDR and →
After I posted my plans for XLR cable tester to Facebook audio DUY group, there was discussion on similar circuits other people has made. Steve Smith wrote (put here with his permission): “If you’re into making your own stuff, this will show up any fault with a mic cable when connected to phantom power. Three →
Building a sound system is often a highly personal process, from deciding what to get, to assembling and using it. Here is my PA system I built in 1990′s and used for some mobile DJing. The need for measurements were that it should fit easily to a normal size car with everything else that is →
I have designed many years a VGA cable based video camera cable which could hande video in two directions (from camera to mixer and return video to cameraman), a two-way voice connection (ClearCom type) and 12V power to the camera. All the signals run along an equally long (tens of meters) VGA cable. These were →
Year 1999 A friend called from a big computer festival Assembly 1999 that was starting. It was one of the biggest this type of event in Europe with thousands of people coming with computers. Some of my friends was running big screen and video streaming for the event. They had all the stuff rented and →
I saw presentation of Sound Tools XLR Sniffer/Sender at https://www.ratsoundsales.com/mm5/merchant.mvc?Screen=PROD&Product_Code=soundtools-xlr-snifsend It was described: “Quickly troubleshoot faulty mic lines and cables with this set of remote end cable testers. The XLR Sniffers can also utilize phantom power to test snake lines and cables in live environments, making it simple to diagnose issues and get your show →
For a passive summing mixer is a circuit to combine two audio signals to one signal. Passive summing works generally ok, both with unbalanced and balanced circuits if all connected circuits are same type (mixed balaced and unbalanced is mixed business if it works as wanted or not). When the devices connected to all inputs →
I was pretty actively in making the Assembly computer festival event and the live TV broadcasts made them in the late 1990′s and early 2000′s (and still somewhat in some later years). Here are some tricks learned on that era: Triax cables are used in TV broadcast industry for TV camera interconnections (connecting camera to →
Here is maybe simplest power over Ethernet (PoE) powered LED Christmas light. This circuit provides powering of LED light string from IEEE 803.2af compatible standard power supply. On the up there is the IEEE 802.3af PoE power supply that feeds 48V DC power to RJ-45 connector when it detects a PoE needing device connected. I →
Found some broken LED christmas lights (operated originally from 24V transformer) and a suitable spare switch mode power supply (36-72V to 24V). Then I got an idea to combine them to an experimental PoE Christmas light project. Circuit diagram: The circuit operation: Initially circuit presents around 23 kohms impedance when low voltage is on line →