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Com-Net Ericsson EDACS Trunking Systems Information

Page Last Updated: 01/23/01

EDACS Talkgroups Conversions
The Uniden EDACS format (which will be called AFS, for (Agency-Fleet-Subfleet):

Using this example (586 DECIMAL = 04-092 AFS = 24a HEX):

(1) 586 decimal = 01001001010 binary  (talkgroups are 11-bit binary)
(2) Split the binary as follows    0100  |  1001  |  010
(3) Convert each group to decimal   04       09       2   
(4) Format as 04-092

The HEX translation would be:

(1) 586 decimal = 01001001010 binary
(2) Split binary as             010  |  0100  |  1010
(3) Convert each group to HEX    2        4        a
(4) Write as  24a

The BC245 can do the DECIMAL/AFS conversion internally, and the
user can choose either mode of entry and display.  So it won't 
be necessary to do this by hand.

Also Available at:
http://www.egroups.com/files/BrevardRadio/Utilities/GEAFS/

EDACS Fleet mapping

Establishing a fleet map structure dictates the max number of agency and fleet calls which can be assigned.  Within the fleet map structure, the more agencies that are setup, the more agency calls that can be assigned.  The same is true for fleet calls.   To enhance each agencies flexibility, you can have different fleet and subfleet structures for each agency to suit specific radio communications requirements

A group call is addresses using a Group ID (GID).  The GID is composed of 11 bits to define a total of 2048 max groups.  The fleet map is structures for each agency to suit their specific requirements.

Some examples of the possible fleetmaps are shown below (similar to Motorola Fleetmaps)

Agencies Fleets Subfleets
2 32 32
2 16 64
2 8 128
2 4 256
4 32 16
8 8 32
8 16 16
16 16 8

The most common fleet map used by EDACS systems is 8 (3 bits) agencies, 16 (4 bits) fleets and 16 (4 bits) subfleets.  If we take a couple of examples of group calls, you can easily see how simple the fleet structure really is.

Using a 3/4/4 structure, we can now partition the 11 bit Group ID (GID) as follows:

_ _ _     /     _ _ _     / _ _ _ _

Agency    Fleet            Subfleet

Binary examples are shown below:

    Agency 1, Fleet 1, Subfleet 1 (GID 273 Decimal)

    0 0 1 / 0 0 0 1 / 0 0 0 1

    Agency 1, Fleet 1, Subfleet 15 (GID 287 Decimal)

    0 0 1 / 0 0 0 1 / 1 1 1 1

A group call for Agency 1, Fleet 1, Subfleet 0 (GID 272) is a Fleet group call. All subfleets in Agency 1, Fleet 1 will respond to the call.  A binary representation is as follows:

    0 0 1 / 0 0 0 1 / 0 0 0 0

When an EDACS radio sees the fleet call assignment (GID 272), it immediately associates Subfleet 0 as being a Fleet call for Agency 1, Fleet 1.  If the radio's channel selector is on a subfleet within Agency 1, Fleet 1, the radio hears the call.

A group call for Agency 1, Fleet 0, Subfleet 0 (GID 256) represents an Agency Group call.  All fleets and subfleets in Agency 1 will respond to the call.  A binary representation is as follows:

    0 0 1 / 0 0 0 0 / 0 0 0 0

When the radio sees the Fleet call assignment (GID 256), it will immediately associate Fleet 0, Subfleet 0 as being an Agency call for Agency 1.  If the radio's channel know is on a subfleet within Agency 1, the radio will automatically hear the call on GID 256.

This type of fleet mapping ensures Agency Fleet calls under failure mode of operation (such if the Site Controller were to fail)

EDACS Misc. Information 
All EDACS systems have 25 real LCN channel frequencies, and then an
additional six 'status' channels that show up under Etrunk.  They are not
actual frequencies, but they indicate a certain status message to the
calling radio.  Here is what I have added to all my EDACS system files.

s  DOWNLINK,1a,ffff,0
s  RESERVED,1b,ffff,0
s  CONVERTc,1c,ffff,0
s  QUEUEDid,1d,ffff,0
s  SYS-BUSY,1e,ffff,0
s  DENIEDid,1f,ffff,0

I'm not too sure about the first two, but CONVERTc is used to tell a radio
who PTTs while there talkgroup is active, and sends them to listen to the
talkgroup, giving them an error beep as well.  QUEUEDid is where a calling
radio will be placed if they are waiting for a next available voice channel
or phone patch, etc.  SYS-BUSY, means the system is busy, no channels
available, and somebody is in the Queue.  DENIEDid is if that radio ID is
not allowed on the system for some reason.
EDACS Equipment Information 
EDACS System Overview

Enhanced Digital Access Communications System (EDACS) is available in VHF, UHF, 800 and 900 frequency bands and wideband (25 kHz) and narrowband (12.5 kHz) configurations.   This spectrum resource provided a springboard for the development of trunking systems.  Public service radio manufactures working with Associated Public-Safety Communications Officers (APCO) developed a requirements document (APCO 16) for trunked radio systems.

EDACS provides coordinated communication between agencies and integrates all services; Dispatch, Secure Voice, Telephone and Data within a single common communication system.   EDACS systems have a single control channel communicating between the system and the field radios.  These configurations range from Basic EDACS to EDACS Level 4, consisting of Voted and Simulcast Systems.  An EDACS  Multisite Network links Systems together via a Multisite Controller (MSC) or Integrated Multisite and Console Controller (IMC).

There are two types of radio channel designations are used in EDACS: One of them is the Control Channel and the other is the Working Channel.  The Control Channel is used to send digital data between sites to the radios.  This data is continually transmitted to the field units.The Working Channels sends voice and data over the air.