A crystal radio is basically a high Q resonator tied to an antenna and an envelope detector. These days the envelope detector is a point contact diode such as a 1N34 Germanium diode. The resonant ...

Before the second world war Radio was a revolution in mass-communication much like the internet today. Fortunes were made and lost ... technology of the first-half of the 20th century!

It was a scant five inches high and used ... radios. In fact, they were going to devote their whole company to commercial products like that. Tsushin Kogyo was close to manufacturing its first ...

As a result, both of these detectors require THz powers of nearly 1 mW, making them several orders of magnitude less sensitive than detectors used in the ... These panels were constructed by ...

However, to understand 10 Codes, it helps to understand the background of the radio and Morse code. The first ... was used ...

They were quiet. Planes were a very new invention, they were rare and fragile. But when World War One started they became weapons. Pilots could spy on enemy targets and the first bombs were ...

1364 - First recorded use of a firearm. 1380 - Hand guns are known across Europe. 1400s - The matchlock gun appears. Before the matchlock, guns were fired by holding a burning wick to a "touch ...

Flame detectors use optical sensors working at specific spectral ranges (usually narrowband) to record the incoming radiation at the selected wavelengths. Typically, 30–40% of the energy radiated from ...

If the X-Sense is unavailable, we also like the First ... use hardwired detectors, you need to physically connect them to achieve this. Battery-powered options, on the other hand, connect via a ...

The first iteration of store cards was known as charge plates, credited with being popularized by the Charga-plate bookkeeping system. These dog-tag style metal plates were used in the 1930s ...

Household appliances and engines that use combustion make CO ... Choose a day each quarter to test your CO detectors, but ...

Get a first look at how the UK's new Official Chart is shaping up this week and see where Friday's new releases have landed.