Other Input Devices

VOICE RECOGNITION

Method

Using a microphone (or a telephone handset) human speech is coded into a sequence of electrical signals. The computer being used searches a set of stored patterns for the sound which has been input.

Advantages of voice recognition

1 No typing or data preparation is necessary.

2 It can be used remotely by telephone, or by those who are handicapped or who have their hands occupied.

Disadvantages

1 At present the method does not give good results. Relatively few words can be recognized and the error rate is high.

2 Recognition is slow.

3 It is not suitable in noisy places without a shielded mouthpiece.

Uses

1 Where only a few different commands are to be given and the hands cannot be used, for examply by a helicopter pilot to produce a display of the appropriate instruments on a screen, using simple prestored voice commands.

2 Over the telephone, for example by a bank. The computer can recognize a caller from a spoken code, tell him/her the state of a requested account ( by synthesized voice ) and accept simple commands such as ‘repeat’.

3 By handicapped people to control equipment..

DIRECT INPUT FROM INSTRUMENTS

Many measuring devices are now digital and electronic and can be linked to a computer. This requires special software to make use of the data coming in and, usually, a special interface between the device and the computer.

Examples of direct input

1 Thermostats or thermometers connected to a computer controlling a heating system.

2 A pressure pad on a road connected to a computer controlling traffic lights.

3 The instruments in a space vehicle interfaced with a computer which calculates the flight path and controls the rockets.

Comparison of Input Methods

Note: Speeds are in characters per second unless otherwise stated, and refer to the rate at which the input device transfers data to the central processing unit.

Input device	Medium	Preparation method	Verification method	Typical input speeds
Disc unit	Magnetic discs	Typed at key station	Retyping at same station	100000 to 2000000
Tape drive	Magnetic tape	Key to tape or pooled from key to-disc station	As disc or by rewinding tape	150000
Floppy disc unit	Floppy disc	Separate key station	Retyping at same station	20000
Magnetic tape	Magnetic tape	Separate key- station	Retyping at same station	Cartridge 2000 to 1 000000;
Cartridge/ cassette unit	cartridge or cassette			cassette 2000 to 20000
OCR device; document reader	Document	Handprinting or typing or computer printer or OCR encoder	Checked by eye	1 to 40 documents per second
MICR device	Document (cheque)	MICR encoder	Not applicable	15 documents per second
Mark sense reader; optical mark reader	Marked card or document	Making pencil marks in pre- printed. ovals or rectangles	Difficult to verify	15 to 600 documents per Minute

Fig 17 Comparison of input methods

Digital Computers

COMMUNICATIONS HARDWARE TERMINALS AND INTERFACES

SOCIAL IMPACT OF COMPUTERS

Other Input Devices