Follow these links to

[Technical Stuff About Trunked Systems ]
[Motorola Type I Systems ]
[Motorola Type II Systems ]
[Motorola Hybrid/Type II-i Systems ]
[Motorola Astro Systems ]
[Figuring Out Talkgroup Codes ]

[Ericsson/GE EDACS Systems ]

A Little Bit About Trunked Radio Systems

First introduced to public safety/local government operations in the early to mid 1980s, trunked radio systems were initially looked upon with some justified skepticism, since the earliest systems suffered some major bugs that needed to be worked out. Once the bugs had been cured, though, it became obvious that trunked systems were ideal for public safety and local government operations, since they allowed improved interagency communication and greater flexibility. This is especially so for large metropolitan areas, where multiple agencies can share a single system and communicate with virtually any other agency with a single radio instead of two or three radios.

Trunked radio systems have a number of advantages and disadvantages:

Some Advantages:
1. All city and/or county agencies can share a single radio system.
2. Improved communication between agencies.
3. Reduced costs for all agencies over the long run.

Some Disadvantages:
1. Greater initial cost.
2. Increased complexity for users initially, especially when advanced features are used.
3. Risk of total loss of communications in the event of a catastrophic system failure.

Trunked radio systems are all identical in that their operation is controlled by a computer, called the Central Controller. All also allow nifty special features such as emergency banners, private/individual (radio to radio) calling, dynamic regrouping (where specified radios are assigned by the dispatcher to a new dedicated private talkgroup), telephone interconnect, and so forth. All also offer "failsoft" mode, in which communications can continue in the event of a controller failure.

To a greater or lesser extent, however, the similarities end there. Motorola and Ericsson systems both dedicate one system channel (the Control Channel) for a data signal that tells the radios in the field what to do; E.F. Johnson systems, on the other hand, use all system fequencies for voice communications, controlling the radios via subaudible data on each voice channel. Each talkgroup in an EFJ system is assigned a primary channel in the system; if that channel is busy, the subaudible data stream tells the user radios which channel is now in use for that particular talkgroup.

All of these systems have certain advantages over the others. E.F. Johnson systems have the advantage of using all channels for voice communications, while Motorola and Ericsson systems dedicate one channel for control data. Motorola Type II systems are far easier to set up, while Ericsson systems continue trunking in the event of a controller failure.

Motorola Type I Systems

Motorola systems are currently found in four general types: I, II, IIi and Astro. Also known as Privacy Plus, Type I is the earliest common form of Motorola trunking. In a Type I system, the system is divided up into 8 equal-sized blocks, each of which can be configured various ways, with each user or group of users being a "fleet", operating on various "subfleets", with a set number of radios per fleet.

Some users may need several fleets, with few subfleets, and many individual radios, while other users may require only a few fleets with many subfleets and fewer individual radios. One of the limitations of a Type I system is that once the system map is programmed into each radio, it cannot be changed unless every radio is reprogrammed.

Motorola Type II Systems

Type II systems are newer, and much more flexible than Type I systems. Rather than the fixed fleet/subfleet arrangement of a Type I system, Type II systems use a flexible arrangement of "talkgroups", each designated by a hexadecimal code which can be programmed for any user in any radio without having to reprogram every radio in the system.

Motorola Hybrid/Type II-i Systems

Hybrid systems are newer Type I systems that allow Type II programming, while Type II-i systems are newer Type II systems that allow Type I programming. However, as far as the TrunkTracker is concerned, they are essentially the same. One thing to keep in mind, though, is that even if a system is listed somewhere as a Type II-i system, the chances are pretty good that is is programmed strictly as Type II. Thus, you should always start out using the default "E2" data type. If you get lots of odd numbers and can't follow both sides of the conversation, then start trying the Type I fleet maps.

Motorola Astro Systems

Finally, Astro systems are the newest incarnation of Motorola trunking. This is similar to Type II trunking, with the exception that the system uses digital modulation for voice transmissions instead of analog. Many Astro systems, though, use digital for police and/or fire only, while city services operate solely in analog mode. While digital modulation is excellent from a radio spectrum efficiency standpoint, at this time there are no scanners available that are capable of converting the digital audio to analog. However, since the APCO 25 digital modulation standard is open, it's probably only a matter of a couple of years before a digital capable scanner is available.

There are several types of Motorola systems available today, each of which offers various feature levels:

• StartSite and StartSite XPress
• Analog, up to 5 channels
• Up to 500 user IDs
• Single site
• SmartWorks
• Analog, up to 7 channels
• Hundreds of user IDs, up to 2048 talkgroups
• Single site, supports APCO-16 public safety features
• Smartnet II+
• Analog and/or digital, up to 28 channels
• Thousands of user IDs, up to 4096 talkgroups
• Single site, supports APCO-16 public safety features
• Smartnet II+ Simulcast
• Analog, up to 28 channels
• Thousands of user IDs, up to 4096 talkgroups
• Multiple (up to 10) sites, supports APCO-16 public safety features
• SmartZone (links multiple Smartnet sites)
• Analog and/or digital, up to 28 channels per site
• Thousands of user IDs, up to 4096 talkgroups
• Multiple (up to 48) sites, supports APCO-16 public safety features
• OmniZone (links multiple SmartZone systems)
• Analog and/or digital, up to 28 channels per site
• Thousands of user IDs, lots and lots of talkgroups
• Multiple (up to 128) sites, supports APCO-16 public safety features

Figuring Out Those Doggone Talkgroup ID Codes.....

The ID codes of Type I and II systems differ dramatically. An example of a Motorola Type I fleet/subfleet display ID is 401-B, which indicates Block 4, Fleet 1, Subfleet B. Because the LCD of the TrunkTracker does not allow differentiating between some numbers and letters, the TrunkTracker displays the above as 401-2.

The advantage to knowing Motorola Type I display codes, especially in conjunction with the list of subfleet names in order as programmed in the radios, is that the Type I ID and name list can aid in selecting a fleet map if one knows approxmately how many fleets and subfleets are in a given block of the system. A Type I system is divided into 8 blocks, each of which is assigned a size code that determines the number of fleets, subfleets and radios each block can handle. Thus, knowing how many subfleets are allocated to a given user can provide useful clues to the size code for a particular memory block on a Type I system. More clues can be provided by knowing approximately how many radios a given user has.

If you are fortunate enough to know the Motorola size code assignments for a given system, here is a conversion chart with Motorola and Uniden size codes as well as number of users, fleets and subfleet to help you set up your TrunkTracker:

* Note 1: Block 0 and Block 7 are only capable of 127 fleets (or 8191 unit IDs for a Type II block).

* Note 2: Each Type I fleet is capable of the total number of subfleets listed plus a "fleetwide" subfleet, for a total of 4, 8 or 16 subfleets. Most "fleetwide" subfleets are only used occasionally, especially in business systems. "Fleetwide" subfleets are displayed on the TrunkTracker as xxx-0.

Type II Systems

An example of a Type II hex code is 18F, which displays as 6384 on the TrunkTracker. Type II systems allow 2048 talkgroups per system (4096 talkgroups when priority monitor is not used), arranged in the following pattern (only the first group is shown):

Each succeeding group is identical, beginning with 1-9, A, B, C, D, E or F. The corresponding TrunkTracker display codes for the above group are:

As you can see from the table above, the TrunkTracker displays talkgroups in a "start at 16, add 32" progression. The exception to this is in a system that does not use priority monitor; in these systems the TrunkTracker displays talkgroups in a "start at 16, add 16" progression. Most public safety systems, however, use priority monitor.

Knowing the hex code for a Type II talkgroup means that one can readily find the TrunkTracker ID code using the scientific calculator found in Microsoft Windows 3.1, 3.11 or 95. Simply enter the hex code in hexadecimal mode (don't forget to add a trailing zero; for example, 18F should be entered as 18F0), and switch to decimal mode. The number displayed is the code that will be displayed on a TrunkTracker.

Another nifty trick for figuring out talkgroup codes is knowing that many systems are laid out in a logical progression. If Fire Dispatch is 16, and the next talkgroups in the list are Fire Tac 1, Fire Tac 2 and Fire Tac 3, then those talkgroups are likely to be codes 48, 80 and 112 in that order. This trick does not always work, however, as some systems were laid out following the hex progression originally but then new talkgroups were added to the system, and programmed into the radios in between the original talkgroups. The newly added talkgroups will not follow the normal hex progression.

Another way talkgroup IDs are displayed in a Motorola Type II system is in the form of a 6-digit 800 number. To convert these to Uniden display, use the following formula:

M6 - 800000 * 16 = Uniden

Using the previous hex code as an example:

800399 - 800000 * 16 = 6384

Finally, if you come across a talkgroup that doesn't quite match the "start at 16, add 32" or "start at 16, add 16" progressions, you may have found a talkgroup using a special function. The added numbers that define these are:

• ID+0 = Normal talkgroup.
• ID+1 = All Talk Group (a Type II "fleetwide" or "all call" function).
• ID+2 = Emergency talkgroup (somebody hit the emergency button).
• ID+3 = Bi-directional talkgroup crosspatch.
• ID+4 = Emergency patch.
• ID+5 = Emergency multi-select.
• ID+6 = ? (may not be used).
• ID+7 = Multi-select (dispatcher broadcast on more than one talkgroup).
• ID+8 = DES/DVP digital encryption) talkgroup.
• ID+9 = DES/DVP All Talk Group.
• ID+10 = DES/DVP emergency talkgroup.
• ID+11 = DES/DVP bi-directional talkgroup crosspatch.
• ID+12 = DES/DVP emergency patch.
• ID+13 = DES/DVP emergency multi-select.
• ID+14 = ? (may not be used).
• ID+15 = DES/DVP multi-select.

A Little Bit About Ericsson/GE EDACS Radio Systems

And now we move on to EDACS systems. Known in the hobby community mainly for their obnoxious and aggravating "scanner-buster" beeps (which can be defeated with a couple of after-market gadgets for your scanner), EDACS systems have some advantages over Motorola systems from an operational standpoint. For example, during "failsoft" (failure of the central controller), Motorola systems go into conventional mode, with each radio channel used as a conventional repeater for several users. All trunking features are lost until the controller is restored. EDACS systems, however, remain in basic trunked mode during failsoft; only special features such as private call and others are lost. This is a huge advantage.

EDACS systems are similar to Motorola Type I systems, in that they use a fleet/subfleet arrangement rather than discrete talkgroups like a Motorola Type II system. Fleets are all arranged in groups of either 4, 8 or 16, but there is no limitation on the total number of radios per fleet.

A major difference between Motorola and EDACS trunked systems is in the manner of channel assignment; this has a definite bearing on the way the BC-245 Trunktracker II is programmed. Motorola control channels send out channel assignments using the FCC channel number to refer to the desired frequency; frequencies can thus be entered in any order in the TrunkTracker, and the scanner will know where the necessary frequency is. EDACS systems, on the other hand, send out channel assignments using a Logical Channel Number assigned to each frequency in a system. The system ID and LCN-to-frequency assignments are programmed into each radio, and the radio uses the Logical Channel Number in it's memory to know where to go when the control channel makes an assignment. This means that channels must be programmed into the Trunktracker II in the proper Logical Channel order, or transmissions will be missed.

How do you determine the correct order? Well, many EDACS systems have the channels assigned in ascending order, lowest frequency to highest, so start with that. You'll probably find that it will work fine. If it doesn't work, you'll have to do a little research. Scan the system frequencies in conventional mode, and make notes of the direction the conversations are assigned frequencies. This works best at night when the system isn't very busy, and it will take a bit of doing, but eventually you'll notice a pattern. Write down the order you figure out and give it a try. Eventually, by dint of trial and error, you'll get it figured out. Of course, if you use the ETrunk program and monitor the system visually it's even easier!

What about EDACS talkgroups? EDACS systems are usually set up divided into agencies, fleets and subfleets; an agency is an entire group of users (for example, fire and EMS), while a fleet is assigned to a specific group of users (a single fire department), and subfleets are the individual communication paths (dispatch, fireground, etc). The BC-245 defaults to what is called AFS (Agency-Fleet-Subfleet) display; while digital display can be selected and used if you so choose, AFS provides some really fascinating functionality, allowing one to monitor an entire agency, an entire fleet, or a single subfleet, simply by altering the way the codes are entered.

For example, Agency 3 can be monitored by entering "03.", and all fleets and subfleets will be monitored (one at a time). Likewise, a fleet can be monitored by entering "03.05." and all subfleets in fleet 03-05x will be monitored. Finally, a single subfleet can be monitored by entering 03-051.

But what to do if you have a list of digital talkgroup codes and would prefer to use AFS? Here's the conversion. Using talkgroup code 586 as an example, enter 586 into your Windows scientific calculator in digital mode, and switch to binary mode. You'll see an 11-bit binary number, all ones and zeroes. If there aren't 11 bits, add leading zeroes until you get to 11. Binary is counted, right to left, as 1, 2, 4 and 8, and so:

(1) 586 decimal = 01001001010 binary  (talkgroups are 11-bit binary)

					8421	8241	421
(2) Split the binary as follows		0100	1001	010

(3) Convert each group to decimal	 04	 09	 2

(4) Format as 04-092

Not really easy at first if you're not too familiar with binary notation, but once you try it a few times you'll get the hang of it.

Next, what about those VHF and UHF trunked systems? Well, EDACS isn't a problem since you're simply entering the channels, but what about those pesky Motorola systems and their base and offset frequencies? First, select trunked programming mode and the system type (E2-Hi or E2-UHF), then the bank. Next, enter all of the system frequencies, from lowest to highest. Then hit "Data", enter the lowest frequency in the system as your base frequency. Hit enter, and select the offset. If all of the system frequencies end in 50 (ie, .950, .450, .150), use 50 kHz; if they are separated by 12.5 or 25 kHz steps, select appropriately.

Figuring these trunked systems out isn't terribly difficult; put a little thought and research into the process, and you'll soon have lots of information at your fingertips.