Technical Content Alert!!! The rule changes discussed below are highly technical. If you’re OK with stuff like “attenuation [must be] greater than the attenuation at 1 kHz by at least: 60 log10(f/3) decibels, where ‘f’ is the audio frequency in kHz”, you should have no problem. Others should proceed with caution.

A couple of years ago we reported on a number of changes made by the FCC to its rules governing Travelers’ Information Stations (TIS), the first changes to the TIS rules since TIS were established in 1977. Now those changes have been tweaked, although not as much as some might have liked.

As noted above, the tweaks are highly technical, so much so that we won’t go into detail here. (There’s a reason we chose law school rather than a career in engineering.) TIS cognoscenti should take a close look at the FCC’s decision for the real nitty-gritty. To summarize:

The filtering requirement for TIS has been changed from 3 kHz to 5 kHz. The expectation is that this should improve the quality of TIS signals to match commercial AM station signals – but TIS operators who might prefer, for whatever reason, to continue to use 3 kHz filters may do so. (The Commission declined to eliminate the filtering requirement entirely.)

The roll-off curve relative to signal attenuation has been adjusted in light of the changed filtering requirement.

TIS audio filters may now be placed either ahead of the transmitter or between the modulation limiter and the modulated stage. Existing gear can be retrofitted by deactivating the old 3 kHz filter (which, under previous rules, had to be placed at the last stage of the audio chain) and adding an outboard 5 kHz filter at the transmitter audio input. Alternatively, manufacturers may redesign their gear to insert a 5 kHz in conformity with the revised rules.

Manufacturers who retrofit their equipment will have to file a Class II permissive change request with the Commission for each model to be retrofitted. The request should list all filters to be used and provide “clear and concise” instructions for TIS operators who wish to perform the retrofit themselves. A licensee may retrofit its own system as long as the licensee has determined that (a) its equipment model has received a Class II permissive change grant and (b) only approved filters are used. Equipment newly designed in accordance with the revised filtering rules will need new FCC certification, as will use of an audio processor to perform the 5 kHz filtering (absent a dedicated 5 kHz filter).

Did we mention that these are all highly technical?

On the non-technical front, the Commission took this opportunity to underscore two separate limits relative to TIS program content.

With respect to weather information, TIS operators are permitted to integrate into their feeds weather information, but only “during times of hazardous or potentially hazardous conditions”. A number of folks thought that it would be a good idea if TIS operators could include weather reports – such as routine NOAA weather broadcasts – into their programming. The Commission had previously rejected this notion, mainly because there are plenty of other available sources of normal, non-emergency weather reporting. However, the FCC has now observed that TIS licensees have “substantial discretion to determine what information is relevant to ‘hazardous or potentially hazardous conditions’ under the Commission’s rules”, which seems to provide some leeway on this front. The Comission helpfully offered the following non-exclusive list of conditions that might justify tapping into NOAA weathercasts: “snow, ice, mudslides, fog, flash floods, thunderstorms, wildfires, tornados and hurricanes”.

And music lovers take note. Responding to anecdotal reports of TIS-transmitted music, the Commission reminded TIS licensees that “music content of any kind is not permitted”.