Issue 2, May 2006

VEMCO to Introduce More Codes for Transmitters

Background
When VEMCO first introduced coded transmitters, 256 unique transmitter IDs were available. As the technology became more popular, this proved to be inadequate so additional coding schemes and standard Code Maps were developed to support a great deal more IDs as well as Sensor Tags. The Map used for 69 KHz (sometimes referred to as Vemco D51-84) is summarized in the Table below. (Follow this link for a background on Coded Transmitters).

In actual fact, Sub Map D was never used for R64K since, for a long time, the 4096 Codes provided by Sub Map B were adequate. Instead, the 340 millisecond interval was used for a number of special cases such as providing an additional R256, R4k or S256 Sub Map for custom installations.

Changes to the 51 kHz to 84 kHz Standard Map
At the VR2 Workshop in November 2006 (See Article in this Newsletter), users confirmed our view that more ID codes are needed to ensure that no situation ever arises when a tagged fish is falsely identified due to use of duplicate codes. Therefore, we are laying the groundwork to make transmitters with R64k coding (i.e. 64k unique IDs) available to users.

To do this, we are redefining the standard Map (to be called Vemco 1.1 2006 51-84) as shown in the table below. This differs from the previous standard in two respects:

1. R256 Pingers are being phased out and Sub Map A reassigned to provide a second S256 Sub Map.
2. The previous Sub Map D, which was unused except for a few custom situations, is redefined as a R64k Sub Map with a 320 millisecond SYNC interval.

At the same time, Sub Maps B and C, which are used by the vast majority of 69 kHz Transmitters sold, have not been changed.

Implications for Users
Wherever feasible, we will encourage users currently using R256 Tags on Sub Map A to move towards R4k Sub Map B) or R64k (Sub Map D). We will continue to support those who need R256 transmitters because they are using VR1 receivers.

Since there are not enough IDs to meet the requirement of all those deploying pingers, Sub Map B needs to be treated as a scarce resource and, therefore, we will be encouraging customers using pingers to move to the 64k Sub Map D.

To meet concerns of users who want to do testing before committing to longer 64k codes, we will try to meet the 2006 needs from the 4k Sub Map B. At the same time, we will ask them to try some 64k tags with a view to committing to R64k for 2007.

The following table summarizes modifications users will need to make to receiver configurations to support these changes.

We will be providing detailed instructions to support users needing to reconfigure their receivers as well as the appropriate configuration files for Vemco 1.1 2006 and selected custom Maps. Users requiring assistance or more information should call 1-902-852-3047 or email Customer Support. As well, users who feel they may require a configuration change before full instructions should also contact Customer Support for assistance.

New Nomenclature to be Introduced

Planned future coding enhancements which will support new capabilities such as more ID Codes, more robust error detection and/or correction, more sensor data (number of sensors, bits per sensor), etc. will not fit very well, if at all, into the "Sub Map" structure. Therefore, we plan to introduce a new nomenclature which will be used for all coding schemes and will provide a unique, unambiguous characterization for each current and future coding scheme ("sub map" in the current definition).

The introduction of this new nomenclature will coincide with the planned release of a new generation of Receiver PC software later this year. More details will be provided in our next Newsletter to be published late this Summer.