Radio Consoles: CSSI v Native P25

The APCO P25 Console Subsystem Interface (CSSI) standard allows dispatch consoles from different manufacturers to be connected to the controller/core of other manufacturers’ P25 radio systems. CSSI is a subset of the ISSI standard interface. For example, a Zetron console could be connected to a Motorola P25 radio system, or an Avtec console could be connected to a Harris P25 radio system. The ability to choose between multiple console vendors creates competition which ultimately is good for customers. Competitive forces tend to drive down prices and inspire product innovation. While CSSI/ISSI interfaces usually lack some core features of the native P25 radio system, they can provide other advantages especially for supporting non-P25 radio systems.

All manufacturers try to use innovation to differentiate their products, so there is a paradox in that all the manufacturers claim to support standard interfaces, but their products typically support many additional features beyond what is defined in the standards. Thus, a radio or console system that only supports features in the CSSI standards would probably lack many other desirable features.

The advantages of third-party CSSI consoles:

  • Typically lower cost than the native consoles offered by the radio system manufacturer
  • Innovations in console architecture that are independent of the P25 radio system
  • Features to support legacy conventional radio systems or non-P25 digital radio systems.

The disadvantages of third-party CSSI consoles are primarily due to the limitations of the ISSI/CSSI interface:

  • Patching, and Simul-select functions with CSSI consoles may take multiple talk paths on the towers, causing busy conditions or dropped audio during major events, whereas a native P25 console only uses 1 talk path per tower
  • Paging or alerting via P25 control channel may not be supported over CSSI, limiting choices on alerting solutions
  • In the event of simultaneous key-ups on the same Talk Group on different towers, a CSSI console will only receive one audio stream, whereas a native system console can usually receive all streams from the core network. These conflicting Radio transmissions are still sent to the native consoles.
  • OTAR encryption key updates may not be supported over CSSI
  • Alias lists (associating meaningful names to radio IDs and talk groups) are not synchronized with network alias lists. Console alias lists must be updated manually on a CSSI console
  • The ability to discretely monitor or record Individual radio calls is not supported on CSSI
  • The exchange of data between console or CAD and radio subscribers may not be supported for some applications via CSSI
  • Some signalling applications like Request-To-Talk queueing may not function over a CSSI interface.

What’s the right type of radio console for your dispatch centre? It depends which capabilities are most important to your operations. If you’re interested in discussing your needs further, or looking for advice on which might be best for your specific application, feel free to contact me directly through the form below.

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