Digital Switching Systems: Architecture and Network Functions
Digital Switching Systems Architecture
Modules with analog connection to the outside of the node:
- User module analog
- Analog trunk module (obsolete)
Modules with digital connection to the outside of the node:
- Digital user module
- Indirect user module
- Liaison with other operators
- Multiprotocol access module
- Digital links module
- Data link module
- Power module
- Interconnection satellite module
- Connection with special networks
- Common channel module
Modules outside the offline node:
- Service circuit module
- Peripheral maintenance module
- User clock module
For final sets, auxiliary control elements are used. This signal differs from the MIC signal by using 16 bits per channel instead of 8, resulting in double the speed.
Communication Paths
- Local exchange: User module initiates communication, network switching, end-user module.
- Outgoing communication: User module establishes the communication, digital switching module link.
- Incoming communication: Link module, digital switching network, called user module.
- Transit communication: Link module, digital switching network, link module.
General structure of a module: The interconnection system, specific module circuit, and control system.
The Switching Network
Features:
- Monitoring is conducted by the lines themselves.
- The network has a mirror structure; all connections are made identically, and the switching elements share the same design.
- The switching elements are identical, facilitating system expansion.
The basic element is the switch, consisting of integrated circuits (switch ports) connected via a time-multiplexed bus. Each integrated circuit is formed by two pairs of mutually independent ports, ready to accept PCM signals. All multiport network (Tx and Rx) components are connected by PCM paths, which go to module ports and are synchronized using the same frequency (8.192 MHz).
Port Specifications
- Receiver port: Destination port memory, destination channel memory, channel state memory, and free output port memory.
- Transmitter port: Data memory and channel state memory.