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
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