Mr. Weitbrecht patented the acoustic modem that linked teletypes over telephone lines.
From the online.wsj.com
The surface unit contains the acoustic reception modem.
From the sciencedaily.com
Chryssostomidis and his colleagues are also working on underwater acoustic communication via modem and on software that enables high-level control of both communication and navigation.
From the sciencedaily.com
According to Vadic, the change in frequency assignments made the 212 intentionally incompatible with acoustic coupling, thereby locking out many potential modem manufacturers.