🚀 go-pugleaf

One of the cheapest ways to digitize and compress speech is with a codec.
These chips are used by the phone company.  They take an audio input and filter
it, digitize it, and compress it into 8-bit samples at an 8 KHz sample rate.
In addition, there is circuitry to convert the digits back to audio.  The
digital I/O is serial.  The parts cost around $5 to $10 in hundreds; I don't
know the single piece price.

There are two standards, mu-law and A-law.  The difference refers to the data
compression algorithm, mu-law being the U.S. phone standard and A-law being the
European standard.  It doesn't matter which one you use-- they both work well.
Codecs are made by many companies, including AT&T, Intel, Motorola, National,
Oki, Fujitsu, and others.

As for storage and retrieval, a cheap microcontroller (e.g., 8051 type) and a
bunch of slow RAM should work fine.  If you want to do any digital signal
processing (e.g., extra data compression), TI's 1st generation DSP, the TMS
32010, can be had for less than $5 (not sure about single piece prices).

-- 
Bill McFadden    Tektronix, Inc.  P.O. Box 500  MS 58-639  Beaverton, OR  97077
UUCP: bill@videovax.Tek.com,  {hplabs,uw-beaver,decvax}!tektronix!videovax!bill
GTE: (503) 627-6920         "The biggest difference between developing a missle
component and a toy is the 'cost constraint.'" -- John Anderson, Engineer, TI