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CATS - Communication And Telemetry System

What It Is

At its core, CATS is a packet radio standard primarily designed for autonomous position reports, but is versatile enough to support a much wider scope of communication. CATS packets are extremely versatile, consisting of multiple "Whiskers" which make up the packet. Whiskers come in several types. For example, a typical CATS position beacon would likely contain an Identification Whisker, GPS Whisker, and potentially a Comment Whisker and Timestamp Whisker. Different Whiskers can be mixed and matched to allow a wide range of data to be encoded. Detailed information on CATS can be found in the standard, linked below.

Comparison to APRS

CATS is ultimately meant to be a replacement to APRS. Although APRS was magnificent when it was first developed, current technology allows us to do better. APRS also suffers from decades of bloat, making the standard difficult to learn. Here are some of the ways CATS is better than APRS:

Design Philosophy


FELINET is, roughly speaking, the APRS-IS equivalent for CATS. FELINET servers communicate with each other and with I-gates to provide a single unified network of CATS packets.

Project Status

CATS is extremely work-in-progress. Most importantly, this means the standard can change in unpredictable ways that potentially aren't backwards compatible! Once things are solidified a bit more, the standard will be locked down and all new changes must be backwards compatible.

At the moment, there's a running FELINET server which gates to and from APRS-IS for backwards-compatibility, as well as an I-Gate and basic mobile transceiver. Packets are transmitted over the air to the I-Gate, then sent to FELINET and relayed onto APRS-IS.

Community Projects


CATS is entirely open, so contributing can be done the normal way by opening issues and PRs on any of the above projects. Another way to contribute is by setting up and playing with CATS hardware. Bug reports and feature requests are extremely important to allow the standard, and reference implementation, to mature.


If you're on Matrix, there is a space for CATS discussion: #cats:crabsin.space

If you have any questions, feel free to email me at cats (at) scd31.com . 73 and hope to catch you on CATS!