Basic modules

S0. Attachment for 4FTR and LCPU

S0. Attachment for 4FTR and LCPU

The S0 attachment is used to connect the DVS-21 to ISDN telephone systems and is conceived for live public address (coming and going).

The S0 attachment can only be used in combination with the carrier card 4FTR or the LCPU. The 4FTR can accept up to four attachments and the LCPU one attachment. E1, S0 and UART attachments can be freely combined on the 4FTR.

At a Glance:

  • Remote (live) public address system on e.g. train platforms
  • Storing of up to 16 call numbers for incoming calls
    • Authentication and prioritizing of the 16 callers using call identification (CLIP)
  • Storing of up to 32 call numbers for outgoing calls
  • Automatic calling of a service number when a malfunction occurs in the system
    • Provides error message from audio databank
  • Acknowledge audio signals to
    • Signal readiness for speaking
    • Signal successful announcement (positive acknowledgement)
    • Signal error message (negative acknowledgement)

The following block diagram illustrates the way the S0 attachment for 4FTR or LCPU functions.

Block diagram for S0 attachment
Block diagram for S0 attachment

The FPGA regulates the S0 flow of data between the S0 attachment and the BusCPU on the 4FTR or LCPU. Here the BusCPU is the interface to the DVS-21 and the S0 attachment the interface to the outside world.

The microprocessor controls the other functions such as e.g. LEDs on the 4FTR.

The display is an aid to programme the telephone numbers for the person doing the commissioning.

Public addressing can be carried out for remote locations with the digital switching system DVS-21 over private and public communications networks. Two typical application examples are shown as follows.

Remote public address on train platformsLoudspeaker
Remote public address on train platformsLoudspeaker

The S0 attachment in the DVS-21 is connected to a basis connection of the ISDN network (Euro-ISDN: protocol E-DSS1). Public addressing can be carried out through other devices connected to the ISDN network.

Remote public over PABX systemsLoudspeaker
Remote public over PABX systemsLoudspeaker

The second example is used typically in industrial applications. For this the telephone system must have at least one ISDN basis connection as interface for the DVS-21 system. Public addressing for remote locations can be carried out here, too, through various devices.

The basic function sequence is the same for both applications.

Function Description:

A call number with an appropriate priority is allocated to each loudspeaker circuit. Up to 16 call numbers can be stored on the S0 attachment for announcements.

An authentication is carried out by comparing the call number of the caller with the stored call numbers.

The DVS-21 system permits allocation of 99 priorities for low frequency (LF) connections. Public address through S0 can be given priority compared to other connections in the system.

Up to 31 call numbers and a service number can be stored for outgoing calls.

A service number is called automatically in the case of disruptions and a stored text message (up to 8 seconds) or a disruption audio signal is sent.

Acknowledge signals indicate whether the system is ready for an announcement or if an announcement was successful.

Announcements are brought to a close either when the caller hangs up, through a pause in speaking, a cancellation of priority or a timeout.

The following flow chart illustrates how an S0 public address system works:


In the second flow chart the process of calling a service number is illustrated:


Arrangement of a DVS-21 for S0 public address:

The DVS-21 public address system has a modular structure. A system can consist of one or multiple 19” attachment racks in which all attachments for control and switching as well as the power supply attachment (input 48/60 Volt) are placed.

A DVS-21 remote public address system includes the following attachments:

  • DC/DC converter Type: SV01
  • Processor Type: CPU1
  • Digital speech memory Type: DSS1
  • Four carriers Type: 4FTR with S0 attachment
  • Universal interfaces Type: 4IOS
  • Amplifier Type: V100

Error message input/output, LF monitoring of the loudspeaker circuits (LC) and LC distribution are realized through 4IOS.

The use of multiple V100s and V100s with disaster function is possible.


For stepped offset public address for other locations, additional systems can be networked through double copper wire (attachment 4NSA/4NPA) or 2 Mbit/s connection (attachment 4FTR with E1 attachment).

This kind of networking allows the announcement to be passed on in a controlled way over S0.

The Front Plate Symbols and their Meaning:

The System Blinker The System Blinker
Addressing from processor taking place
I/O Input/Output
BUS output works as push-push operation with the system blinker
BUS input works as push-pull operation with the system blinker
On Channel Active
Live public address (LF)
Al Error in Attachment
(Card related display)
The System Blinker Receiving: Control Data from External Interface
(Card related display)
The System Blinker Sending: Control Data to External Interface
(Card related display)

Technical Data:

Operating Voltage: +/-5 V (control)
Operational Current (+5V) xx mA
Operational Current (-5V) xx mA
Interface: Euro ISDN
Protocol: E-DSS1 (based on ITU-T I.411)
Temperature Range: 0 °C to 45 °C
Weight (4FTR): 155 g
Weight (S0 Attachment): xx g per attacment g
Installation Height (4FTR): 3HE
Installation Width (4FTR): 6TE
Dimensions (S0 Attachment): 34 mm x 80 mm (height x width)
Number of Modules: 4FTR: up to 4 attachments
LCPU: 1 attachments