Charactron

From Wikipedia, the free encyclopedia

Charactron was U. S. registered trademark (number 0585950, 23 February 1954) by Consolidated Vultee Aircraft Corporation Convair for its shaped electron beam cathode ray tube. Charactron CRTs performed functions of both a display device and a read-only memory storing multiple characters and fonts.

The term Charactron is sometimes mistakenly applied to another type of CRT properly called a monoscope which generates an electrical signal by scanning an electron beam of uniform cross section across a printed pattern on an internal target electrode.

There were two types of Charactrons:

Video scan: not meant for direct display, these instead generated data in the form of electrical pulses that could be combined with a video signal and then displayed on other devices (including other CRTs)^{[citation needed]}
Direct view: contained dual sets of deflection plates, one to select the character and another to position it on the phosphor screen; these were used as computer and radar displays and as highspeed computer photo printer devices

Essentially, it used an electron beam to scan a specially-patterned anode that contained the dot patterns for each of the characters that it could form. The gross positioning of the electron beam selected among the many characters that could be formed and fine scanning of the electron beam was then used to read out the bit pattern of the selected character (in direct view Charactrons a wide electron beam was used that covered an entire character's matrix at the same time, no "fine scan" was needed).

Because the electron beam was steered electrostatically, access time to the individual character data was very fast.