Comital Emergency Code

The Comital Emergency Code (CEC is an emergency communication system originally used in the city of Barcelona, and later extended to other parts of the Mediterranean Crown. It uses a system of underground pipes that, when activated, let in seawater and create vibrations that can be both felt and heard. It was originally meant for emergencies only, but the code used in Barcelona specifically has developed to a point where complex messages can be conveyed as well.

Morphology

The CEC isn't a fully-fledged language, nor is it a code to represent another language. Instead, it's its own complex system of one-way communication, capable of communicating relatively complex ideas within its designated scope. The messages are sent from government-controlled buildings by highly specialised government officers.
Sound and touch are both used in the CEC. Both systems are redundant for the most basic messages, meaning that the basic meaning is conveyed both with vibrations and sound. This meaning is conveyed through specific rhythmic patterns, following this structure:

Mouse over each item to see an explanation
attention — category — severity — time — area — instructions — end

The system is designed so that the most urgent messages take as few time as possible. For example, high severity is marked with a single short and intense vibration.
The vibration patterns are accompanied by loud sounds that follow the same rhythm, so one can hear the message while in a place not covered by the underground pipe network. In addition, tonal patterns are also used to express more nuanced messages. For example, when giving the instruction to stay at home, tones can be used to communicate additional instructions, such as locking the doors, staying clear of windows, or going to the upper floors of a building.

Standardization and Updates

All CEC systems in the Mediterranean Crown must use the same patterns, with the exception of area codes, which are location-specific. The the patterns and basic usage policy of the CEC is laid out by the Office of Public Communication (OPC) and adapted by each city to its own local policy.
The OPC publishes updates to the code regularly, every one or two years on average, which means that most people don't fully understand all the nuances of the messages sent through the system. However, this isn't usually a problem, as the system is designed in a way that you can always understand the basic meaning even if you don't get the nuances.

Out of all the wacky technology on Earth, this one must surely be one of the wackiest. Of course, I could say the same of so many other inventions in this planet.

— From Min-aniara Laita's travel journal.

Used in

Major cities along the coast of the Mediterranean Crown

Creation

1805 (Barcelona)

noise complaints

In recent years, the amount of complaints against the use of the CEC system has been on the rise. The introduction of the trivial severity level meant that the government began using the system for non-emergency public service announcements. Given that when the system is used the entire city shakes, this proved incredibly uncomfortable for many people.

Some years ago, the OPC started to redesign the system to address this complaints. The current iteration allows for control over which areas of the city receive vibrations with a great deal of accuracy. According to the updated policy, trivial communications can only vibrate in public spaces at low intensity, and no vibrations should be felt in private property.

Of course, this doesn't address the noise concerns. No matter how low the vibrations are, the sounds are still heard all around the city—otherwise the system would be pointless.