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.
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.
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.
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..
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.
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.
| 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
Labels: Computer