Electrocommunication

Electrocommunication is the communication method used by weakly-electric fish. Weakly-electric fish are a group of animals that utilize a communicating channel that is "invisible" to most other animals: electric signaling. Electric fish communicate by generating an electric field that a second individual receives with its electroreceptors. The fish interperets the message using the signal's frequencies, waveforms, delay, etc
Some of the Syreni who are related to these weakly-electric fish also have this ability along with any Syreni who has gone into a symbiotic relationship with such a fish and is able to use them as their communication tool in exchange for food, protection and shelter. Every Syreni have such a relationship and it is not just allowed for a special group or the elite. But they are so useful that most upper class Syreni have one. 
There are also some fish and Syreni who can only send out or receive information through an electric field but not both. 
Weakly-electric fish like that would be the Peters' elephantnose fish (Gnathonemus petersii) and the black ghost knifefish (Apteronotus albifrons) and the males of the nocturnal Brachyhypopomus pinnicaudatus, a toothless knifefish native to the Amazon basin, give off big, long electric hums to attract a mate as well.
The electric organ discharge waveform takes two general forms depending on the species. In some species the waveform is continuous and almost sinusoidal (for example the genera Apteronotus, Eigenmannia and Gymnarchus) and these are said to have a wave-type electric organ discharge. In other species, the electric organ discharge waveform consists of brief pulses separated by longer gaps (for example Gnathonemus, Gymnotus, Leucoraja) and these have a pulse-type electric organ discharge
Electrocommunication is not all these fish and Syreni can do. By creating an electric field they also gain the ability of electrolocation aka object detection even if said object is buried beneath sand or hidden behind walls.