HVAC Control in the New Millennium.pdf - HVAC.Amickracing

HVAC Control in the New Millennium• prerecorded messages produced by human voices,• digitized words produced by human voices and• phonic integrated circuits.Early electronic speech units used tape recordings of a humanvoice. The human voice is an analog form of energy made up of a mixtureof tones. If prerecorded messages are stored on a single magnetictape, the tape will have to be searched each time for the correct message.This time delay could be a problem in an emergency.Samples of prerecorded human voice output are still used in sometoys. A miniature record is used. Digital audio recordings can use acompact disk for high-quality sound, and a large amount of memory canbe accessed in less than 1 second.A system that uses a digitized human voice is able to store thesounds in computer memory, like any other digital information. Thesounds made by a human being are converted and stored as digitalinformation.A National Semiconductor digitized human voice system calledDigitalker used from 3 to 5 special ICs along with several support ICsfor address selection and audio amplification. The main IC was aMM54104 microprocessor-based controller. The ROM ICs held a total of274 words. Any message made up of these words can be spoken by theDigitalker. Special ROMs are used to satisfy a specific application.The Digitalker interfaces to a personal computer through a parallelprinter port. Programming the Digitalker involves sending it a series ofhexadecimal addresses of words that are to be spoken. The addresses forthe proper pauses between words must also be included.An inexpensive way of producing speech output for machines is touse phonic integrated circuits. A phonic integrated circuit uses phonemeswhich are the smallest distinct units of speech to produce speech.A typical phonic integrated circuit may have 64 phonemes, whichincludes 5 different lengths of pauses. The other 59 phonemes are thesounds such as “OY” in boy and “AY” in sky. See Table 6-1.A processor and an audio amplifier forms a working system withthese ICs. A sound is produced by giving the processor the address ofthe desired phoneme. By giving the processor a series of addresses, youcan produce words and sentences. To produce the word MAY, for example,you could address an MM, as in milk, and then an EY, as inbeige.©2001 by The Fairmont Press, Inc. All rights reserved.