The Enhanced Digital Access Communication System (EDACS) is a

radio Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...

communications protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer science), sem ...

and product family invented in the

General Electric Corporation General Electric Company (GE) was an American multinational conglomerate founded in 1892, incorporated in the state of New York and headquartered in Boston. Over the years, the company had multiple divisions, including aerospace, energy, ...

in the mid 1980s. The rights were eventually bought by

Harris Corporation Harris Corporation was an American technology company, defense contractor, and information technology service (economics), services provider that produced wireless equipment, tactical radios, electronic systems, night vision device, night visi ...

, which eventually stopped manufacturing these devices in 2012, and ended all service in 2017.

History

A young designer, Jeff Childress, created an autonomous radio base-station controller, known as the GETC (General Electric Trunking Card). The GETC was a general-purpose controller with input/output optimized for radio system applications. Childress and the team demonstrated that a smart controller could be adapted to a variety of applications, but his interest was really in

fault tolerance Fault tolerance is the ability of a system to maintain proper operation despite failures or faults in one or more of its components. This capability is essential for high-availability, mission-critical, or even life-critical systems. Fault t ...

. The EDACS system architecture supported large communications footprints. By making the GETC's "trunk" among themselves, one GETC per channel, the system was designed to be inherently fault-tolerant. This provided substantial hardware reductions, and the required software efforts yielded a variety of unique features and options. This was not a new concept in systems design; however, few other teams have embodied it cleanly into such wide distribution.

Software

Software for system managers and radio monitors alike has been developed outside of the vendor. ETrunker is a modification to the Trunker code to work on the EDACS control channel. Users of the software can monitor and log complete system activity. See th
Trunker Site
for more info.

Digital Voice Modes

The first digital voice mode developed for EDACS was GE's Voice Guard, utilizing sub-band coding for its datastream at a rate of 9600 bps. Voice quality was not great, however, with it quickly being replaced by AEGIS. AEGIS was the second generation EDACS digital voice mode, made once again by GE, with Adaptive Multiband Encoding as its coding scheme. The voice quality was supposedly 10 times better than Voice Guard, but it was still not very great, especially compared to ProVoice. ProVoice is

Tyco Electronics TE Connectivity plc is an American-Irish domiciled technology company that designs and manufactures electrical and electronic components. It serves several industries, including automotive, aerospace, defense, medical, and energy. TE Connecti ...

' (formerly M/A-COM,

Ericsson (), commonly known as Ericsson (), is a Swedish multinational networking and telecommunications company headquartered in Stockholm, Sweden. Ericsson has been a major contributor to the development of the telecommunications industry and is one ...

and GE) implementation of IMBE digital modulation for radio communications, being the third generation of EDACS digital voice. It is not APCO-25 compliant, but does use the same IMBE

vocoder A vocoder (, a portmanteau of ''vo''ice and en''coder'') is a category of speech coding that analyzes and synthesizes the human voice signal for audio data compression, multiplexing, voice encryption or voice transformation. The vocoder wa ...

developed by Digital Voice Systems, Inc. (DVSI). The technical difference between ProVoice and the APCO Project-25 standard is how error correction and modulation is provided to transmit the data.

References

External links

EDACS ExplainedFlorida Statewide Law Enforcement Radio System (SLERS)Harris Corporation website
{{Trunked radio systems Trunked radio systems Speech codecs