Voice Systems:

Speech recognizers are utilized in some graphics workstations as input devices to accept voice commands. The voice-system input may be utilized to initiate graphics operations or to enter data. These systems operate through matching an input against a predefined dictionary of words and phrases.

A dictionary is set up for a specific operator by having the operator speak the command words to be utilized into the system. Each word is spoken many times, and the system analyzes the word and establishes a frequency pattern for that word in the dictionary along with the corresponding function to be performed. Afterwards, when a voice command is given, the system seeks the dictionary for a frequency-pattern match. Typically Voice input is spoken into a microphone mounted on a headset .The microphone is designed to minimize input of other background sounds. If a different operator is to utilize the system, the dictionary should be reestablished with that operator's voice patterns. Voice systems contain some advantages over other input devices, as the attention of the operator does not have to be switched from one device to another to enter a command.

A passive graphics device simply draws pictures under computer control; that means it permit the computer to communicate graphically with the user. Examples are dot matrix printers, pen and ink plotters, an electrostatic plotter, film recorders and storage tube refresh and raster CRT displays.

An active graphics device permits the user to communicate with the computer graphically. Generally, it implies that the user is supplying coordinate information in some indirect manner that means by means other than typing the suitable numbers. Typically an active graphics device contains the ability to reposition the cursor & read its new position.