The first television set I ever saw appeared in our house in about 1950. It looked like this - except it was in a box, obviously. My dad had built it from a kit. They made their own entertainment in those days. There was only one channel - BBC - broadcasting on 45 MHz. The programmes were rubbish, the picture was a grainy black and white on a 9` t
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ube, and yet my brother and I were entranced. It was the most amazing thing we had ever seen. Moving pictures! Right there in our living room! Some pedants refer to valves as `thermionic` valves, to distinguish them from the valves plumbers fit, whilst Americans know them as `vacuum tubes`. They look like oddly shaped light bulbs, or fat metal tubes. There are six of them visible in the picture. (OK, Don, seven if you count the CRT). Think of a plumber`s water valve, or a tap. It`s basically a pipe with an adjustable vane inside it. The vane can be rotated from outside the pipe between fully closed and fully open. You can control precisely how much water flows through the valve by adjusting the angle of the vane. A valve like those in the TV set works by controlling the flow of electric current. The key point is that both types of valve allow an external force to influence what`s happening inside. These valves control electric current. A current is a stream of electrons, all flowing in the same direction. So a valve needs a source of electrons, a target for them to aim at, and a force to move them. Plus, of course, a means of controlling how many electrons are moving. Engineers needed a way of thinking about a valve without worrying about unnecessary details such as its physical size or the actual shape of its components. They came up with a descriptive symbol. I found this version in the March 1923 edition of Modern...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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