Etrunk 3.7 Documentation

Origins

Some time ago there appeared on USENET a program and its source code that provided the rudimentary ability to decode Motorola Type I, II, and IIi trunking radio system data. That program was nurtured and refined by a number of contributors. Then, a rudimentary program for decoding Ericsson EDACS data channels was posted to USENET. That rudimentary program was used to investigate further the parts of the data stream necessary to adapt Trunker to EDACS systems. This document represents the results of merging those two efforts. 80% of the code and features is shared by both Trunker and Etrunk.

Current Feature Status

This software provides a rudimentary implementation of Trunker for EDACS. It differs from the Motorola Trunker in the following ways:

• Because EDACS system IDs are limited in size and not necessarily unique in an area, it may be necessary to run ETRUNK from a different directory for each system you monitor.
• ETRUNK does not recognize complex call types (more than 2 user IDs and/or more than one group ID.)
• While ETRUNK works on a single-channel EDACS system, where a single frequency alternates between control channel and voice channel, the 'delay' feature is not functional for those systems.
• Unlike Trunker, ETRUNK does not yet adapt to multiple repeater sites for the same networked system. It will recognize that it is monitoring a networked system, but will not swap out the repeaters files the way Trunker does.
• Because EDACS systems do not utilize standard bandplans, it will be necessary to manually identify all frequencies associated with the EDACS system and update ETRUNK's data files with the LCN to Frequency mapping.

Even with this reduced feature set, a user of ETRUNK should be able to monitor a EDACS system, collect information about talkgroups and radio IDs, and track both individual and group calls.

Please Start by Reading the Motorola (Trunker) Documentation

Etrunk is so much like Trunker, please start by reading the Trunker document, then see subsequent sections about how ETRUNK may be different...

ETRUNK and Commercial Trunking Radios

Since there is currently no (inexpensive) EDACS trunk-tracking scanner on the market, ETRUNK (and its predecessor, EDACS.EXE) are the only way to track conversations on EDACS systems. The GE/Wiz scanner attachment does not track actual conversations, only allows the scanner to detect the end of the conversation on the current frequency. The next one it detects may not have the same call on it.

Use of System ID (SysId) as Primary Index

Like its partner, Trunker, ETRUNK uses a system identifier to associate data files with trunked systems. Since these identifiers may not be unique within a geographical area, it may be necessary to keep a working directory for each unique EDACS system you monitor, and it will probably not be practical to jump from one system to the next without stopping Etrunk.

Networked Radio Systems

Larger EDACS systems share group and radio IDs. Support for networked systems is not presently available. Each repeater in the system is treated as a separate system.Until ETRUNK can distinguish between repeaters, it will be necessary to switch the proper xxxxSYS into the directory with the common group and radio data files.

Handling Bandplans for Each EDACS System

No standard bandplan is available to map LCNs to frequencies. A manual approach is required to determine the frequencies and update the ETRUNK data file.

1. With no xxxxSYS.TXT file in the current directory, start ETRUNK.
2. Once all of the LCNs associated with the system appear on screen, exit ETRUNK with the 'Q' command.
3. Edit the xxxxSYS.TXT file. Change all of the hex frequencies (e.g. 0x001...0x007) with the corresponding frequency in a F8.4 format (e.g. 855.0200).
4. Save the file.
5. Run ETRUNK again and monitor or track the system as desired.

Here is a sample xxxxSYS.TXT file for an EDACS system:

Clinton County,Ohio EDACS System
MAP=00000000
PLAN=0
  v866.2375,1,ffff
 dv866.7250,2,ffff
  v867.2250,3,ffff
 dv867.7250,4,ffff
  v868.1875,5,ffff

Meanings and Possible Values of Key Fields, where different from Trunker

Requirements

• ETRUNK only operates effectively under MS-DOS at this time.
• One must understand that decoding and interpreting data at 9600 bits-per-second and looking up records for thousands of groups and IDs places a certain demand on a CPU. Please don't feel slighted if your 386 or 486 system can't handle the demands of ETRUNK.

Quality of Signal

If you cannot achieve sufficiently good reception to reach 90% accuracy on the data channel, you will be losing information and may have difficulty receiving the audio as well. The EDACS version of Trunker provides a spinner in addition to the blinking '@' sign; both show up when you turn on the 'F'rameIndicator command. If things are working well the spinner should reach a vertical position every second. Slower progress means quality is degraded, perhaps by trying to run ETRUNK under Windows, or because of poor radio reception. Under degraded conditions, ETRUNK will lose some calls and may not show calling radio IDs.