5ESS Switching System

The SM performs multiplexing, analog and digital coding, and other work to interface with external equipment.

Each has a controller, a small computer with duplicated CPUs and memories, like most common equipment of the exchange, for redundancy.

Distributed systems lessen the load on the Central Administrative Module (AM) or main computer.

[citation needed] Power for all circuitry is distributed as –48 VDC (nominal), and converted locally to logic levels or telephone signals.

T-carrier spans are terminated, originally one per card but in later models usually two, in Digital Line Trunk Units (DLTU) which concentrate their DS0 channels into the TSI.

Newer SM's have DNUS (DS3) and Optical OIU interfaces (OC12) with a large amount of capacity.

The Administrative Module (AM) is a dual-processor mini main frame computer of the AT&T 3B series, running UNIX-RTR.

Disk drives were originally several 300 megabyte SMD multi-platter units in a separate frame.

The Administrative Module is built on the 3B21D platform and is used to load software to the many microprocessors throughout the switch and to provide high speed control functions.

5ESS uses a time-space-time (TST) topology in which the Time-Slot-Interchangers (TSI) in the Switching Modules assign each phone call to a time slot for routing through the CM.

The standalone VCDX was also capable of serving as a switch for very small wire centers (a CDX- Community dial office) of fewer than ~400 lines.

An RSM has a limited distance and can serve parts of a larger metro area or rural offices.

Both the RSM and ORM is often used as a Class-5 wire center for small to medium towns hosted from a 5ESS located in a larger city.

As with any SM, the size is dictated by the number of time slots needed for each peripheral unit.

The 5ESS was originally U.S.-only and the international sales resulted in a complete development system and team, in parallel to the U.S. version.

Customisation around the vi and Emacs text editors allowed developers to work with the appropriate view of a file, hiding the parts that were not applicable to their current project.

So, for the gr (generic retrofit) subsystem, the first MR created for the 2371242 IMR, destined for the 'F' load, would be gr2371242aF.

The system always built everything, but used checksum results to decide if a file had actually changed, before updating the build output directory tree.

This provided a huge reduction in build time when a core library or header was being edited.

Most service orders, however, are administered through the Recent Change Memory Administration Center (RCMAC).

In the international market, this terminal interface has localization to provide locale-specific language and command name variations on the screen and printer output.