[Coco] Re: History of Tandy/Radio Shack Cassette Recorders

[Torsten Dittel]

> It is entitled "Data Synchronization Apparatus"

Interesting that this technic got its own "CoCo" patent. For me it looks
like a common "frequency shift keying (FSK)" modulation:

>> Frequency-shift keying (FSK) is a method of transmitting digital signals. The two binary states, logic 0 (low) and 1 (high), are each represented by an analog waveform. Logic 0 is represented by a wave at a specific frequency, and logic 1 is represented by a wave at a different frequency. A modem converts the binary data from a computer to FSK for transmission over telephone lines, cables, optical fiber, or wireless media. The modem also converts incoming FSK signals to digital low and high states, which the computer can "understand."

The FSK mode was introduced for use with mechanical teleprinters in the
mid-1900s. The standard speed of those machines was 45 baud, equivalent
to about 45 bits per second. When personal computers became common and
networks came into being, this signaling speed was tedious. Transmission
of large text documents and programs took hours; image transfer was
unknown. During the 1970s, engineers began to develop modems that ran at
faster speeds, and the quest for ever-greater bandwidth has continued
ever since. Today, a standard telephone modem operates at thousands of
bits per second. Cable and wireless modems work at more than 1,000,000
bps (one megabit per second or 1 Mbps), and optical fiber modems
function at many Mbps. But the basic principle of FSK has not changed in
more than half a century. <<

(from:
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci213936,00.html
)

I'll look up the patent later to find out what's so special regarding
the CoCo.

Regards,
Torsten