The signal generators are horns that have been specially designed for use in rail vehicles pursuant to UIC644. You can playback MP3 audio files and import them on an USB stick. There are modern Class D high-performance amplifiers in the device to allow a 200W sinus output to be generated for the horn. It is even possible to call up a smaller 25W output to trigger e.g. door signals. All signals are tripped by 12 opto-decoupled switch inputs.
The signal generators can be configured using a PC-Service-Tool to, for instance, set a night reduction. There is enough space in the 2 GB internal memory to store MP3 files for everyday use.