T4

T4 or T-4 may refer to:

In airports and airlines

In biology and medicine

In entertainment

In computing

In software and video games

Electricity production

Rail transport

Vehicles

Fax

Fax (short for facsimile), sometimes called telecopying or telefax, is the telephonic transmission of scanned printed material (both text and images), normally to a telephone number connected to a printer or other output device. The original document is scanned with a fax machine (or a telecopier), which processes the contents (text or images) as a single fixed graphic image, converting it into a bitmap, and then transmitting it through the telephone system in the form of audio-frequency tones. The receiving fax machine interprets the tones and reconstructs the image, printing a paper copy. Early systems used direct conversions of image darkness to audio tone in a continuous or analog manner. Since the 1980s, most machines modulate the transmitted audio frequencies using a digital representation of the page which is compressed to quickly transmit areas which are all-white or all-black.

History

Wire transmission

Scottish inventor Alexander Bain worked on chemical mechanical fax type devices and in 1846 was able to reproduce graphic signs in laboratory experiments. He received patent 9745 on May 27, 1843 for his "Electric Printing Telegraph."Frederick Bakewell made several improvements on Bain's design and demonstrated a telefax machine. The Pantelegraph was invented by the Italian physicist Giovanni Caselli. He introduced the first commercial telefax service between Paris and Lyon in 1865, some 11 years before the invention of the telephone.

Technician fourth grade

Technician Fourth Grade (abbreviated as T/4 or TEC4) was one of three United States Army technician ranks established on January 8, 1942 during World War II. Those who held this rank were often addressed as Sergeant. Technicians possessed specialized skills that were rewarded with a higher pay grade. These skills could be directly related to combat, such as those skills possessed by a tank driver or combat engineer, or skills possessed by those in support functions such as a cooks or mechanics. Depending on his or her function, he or she might be called upon by an officer to command a group of men for a specific task. They were non-commissioned officers, as were sergeants. Initially, they shared the same insignia but on September 4, 1942, the three technician ranks were distinguished by a block "T" imprinted below the standard chevrons. Unofficial insignia using a technical specialty symbol instead of the T were used in some units.

See also