SG-2000 MANUAL
114
The SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA
©1995, SGC, Inc.
TEL: (206) 746-6310 FAX: (206) 746-6384
18.0 ALE and Adaptive
Controllers
AUTOMATIC LINK ESTABLISHMENT - ALE
N O T I C E :
The SG-2000 radio as described in this manual is not a controlled export item.
ALE controllers provided by SGC or other vendors which incorporate link
protection systems
are
export controlled technology.
THE EXPORT OF THESE
ALE CONTROLLERS REQUIRES A STATE DEPARTMENT EXPORT
LICENSE. SGC WILL NOT SHIP ALE EQUIPMENT TO DESTINATIONS
OUTSIDE THE UNITED STATES AND ITS TERRITORIES WITHOUT
APPROPRIATE DOCUMENTATION IN FILE AT SGC HEADQUARTERS ON
BELLEVUE, WASHINGTON.
This section provides information on serial port operation of the SG-2000 and is
directed toward users of ALE and adaptive HF radio controllers. The infor-
mation in this document, however, applies to all serial port applications based on
the SG-2000 platform. This section is not intended as a definitive ALE operations
manual; that is contained within the SGC HARDLINK™ ALE documentation .
ALE is a technology which was defined by the MITRE Corporation, a federally
funded non-profit research and development corporation in Washington, D.C. as
Federal Standards 1045 through 1049 and in the Military Standard 188-141A.
The ALE technology relies on the marriage of two new technologies: multi-
frequency modems and digital signal processing.
Where normal radio teletype modems send two tones, which are turned off and
on, or shifted in frequency to achieve data communications, the multi-frequency
modem within an ALE controller uses eight tones spaced 250 Hz apart and
extending from 750 to 2500 Hz in the audio range.
By interleaving data between tones, and by turning tones on and off in particular
sequences (called Golay interleaving) the integrity and recoverability of the
information is greatly enhanced. Then, by using a digital signal processor to
recover the tones, exceptionally robust data communications is achieved in
conditions where a normal signal (either voice or CW) would not be recoverable.