ErvoCom's Passenger Announcement System comprises of the Rail Communication SoftSwitch (RCSS2170), which handles the switching and distribution of audio streams, as well as managing the audio amplifiers (PAS2171, PAA2171). All components are connect via Ethernet cables, allowing for on-demand scalability of the system. The Rail Communications SoftSwitch synchronizes audio across all audio amplifiers, ensuring echo free audio. Any VoIP capable telephone, SOS Points or other VoIP capable devices can be connected with switching computer by Ethernet and used as an audio source.
The Rail Communication SoftSwitch is responsible for the distribution of audio streams through-out the system. Each audio stream is categorized and played based on the stream priority. Since audio is handled digitally, it is possible to enhance and extend the system incrementally, adding additional audio sources and newer functions as needed. Individual amplifiers can be controlled independently, allowing for features such as direct addressing of individual passenger carriages. The volume levels can be automatically adjusted based on criteria such as ambient noise or trains speed.
Digital audio streams from the Rail Communications SoftSwitch are converted by the amplifier into analog, passed through a power amplifier to be played out of loudspeakers. In addition to a digital audio interface, the amplifier is outfitted with a UIC Interface which, as an example, serves redundancy or in the case of fires, provides analog based audio transmission as per the UIC Standard.
The PAS2171 can be used for retrofitting a classical system where the amplifier is typically located in the motor car of the train and provides audio for the entire train. In this configuration, the audio is distributed over the 100V-Technology lines.
The PAA2171 is deployed in trains for a decentralized public announcement system, with each passenger carriage having its own amplifier with direct attached loudspeakers. This eliminates the need for distributing the audio via 100V lines. This has the clear advantage that the analog audio lines don't have to pass over inter-carriage couplings, and means a lower signal interference and significantly improved audio quality.