Electrical telegraphy in the United Kingdom

In the nineteenth century, the United Kingdom had the world's first commercial telegraph company. British telegraphy dominated international telecommunications well into the twentieth. Telegraphy is the sending of textual messages by human operators using symbolic codes. Electrical telegraphy used conducting wires to send messages, often incorporating a telegram service to deliver the telegraphed communication from the telegraph office. This is distinct from optical telegraphy that preceded it and the radiotelegraphy that followed. Though Francis Ronalds first demonstrated a working telegraph over a substantial distance in 1816, he was unable to put it into practical use. Starting in 1836, William Fothergill Cooke, with the scientific assistance of Charles Wheatstone, developed the Cooke and Wheatstone telegraph. The needle telegraph instrument suggested by Wheatstone, the battery invented by John Frederic Daniell, and the relay invented by Edward Davy were important components of this system.

Iterative impedance

Iterative impedance is the input impedance of an infinite chain of identical networks. It is related to the image impedance used in filter design, but has a simpler, more straightforward definition

Richards' theorem

Richards' theorem is a mathematical result due to Paul I. Richards in 1947. The theorem states that for

Mode (electromagnetism)

The mode of electromagnetic radiation describes the field pattern of the propagating waves. Electromagnetic modes are analogous to the normal modes of vibration in other systems, such as mechanical systems

Clydesdale Motor Truck Company

The Clydesdale Motor Truck Company was a motor company that existed from 1917 to 1939 with headquarters in Clyde, Ohio. Initially, they made military trucks for World War I. Military contracts continued to be a large part of their business after the war

Two-tone testing

Two-tone testing is a means of testing electronic components and systems, particularly radio systems, for intermodulation distortion. It consists of simultaneously injecting two sinusoidal signals of different frequencies (tones) into the component or

Vallelunga (South Tyrol)

Vallelunga is a valley in South Tyrol, Italy. It is a side valley of the Venosta Valley. There is a small village in the valley, also named Vallelunga. In 2002-2003 it had an adult population of 339

Frog galvanoscope

The frog galvanoscope was a sensitive electrical instrument used to detect voltage in the late eighteenth and nineteenth centuries. It consists of skinned frog's leg with electrical connections to a nerve. The instrument was invented by Luigi Galvani and

Feuer (surname)

Feuer is the German language word for fire. From its origins, the word "feuer" has made its way into contemporary use as a family name

Cassini Grid

The Cassini Grid was a grid coordinate system used on British military maps during the first half of the twentieth century, particularly during World War II. The referencing consists of square grids drawn on a Cassini projection. For a period after the

Inzer (surname)

Inzer is a surname. People with that surname include:Drew Inzer, American football offensive lineman James C. Inzer (1887–1967), 16th Lieutenant Governor of Alabama William H. Inzer (1906–1978), Justice of the Supreme Court of