5ESS switch

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The 5ESS Switch is the Class 5 telephone Electronic Switching System sold by Alcatel-Lucent. This digital central office telephone circuit switching system is used by many telecommunications service providers.

1 History
2 Architecture
3 Administration
4 See also
5 References

[edit] History

The 5ESS Class 5 Switch first appeared in Seneca, Illinois (815 Area Code) in 1982, slowly replacing the 1ESS switch and other systems in the 1980s and 1990s. The 5ESS was also used as a Class 4 telephone switch or as a mixed Class 4/5 in markets too small for a 4ESS switch. Approximately half of all U.S. telephone exchanges are serviced by 5ESS switches. The 5ESS is also exported internationally, and manufactured outside of the U.S. under license.

Lucent Technologies (now part of Alcatel-Lucent) was formerly the AT&T Network Systems division of AT&T, which in turn was formerly known as Western Electric. The 5ESS came to market as the Western Electric 5ESS, and was most recently marketed under the Alcatel-Lucent name.

[edit] Architecture

The 5ESS runs on a Time-Space-Time (TST) topology. The Time-Slot-Interchangers (TSI) in the Switching Modules (SM), one per several hundred to few thousand telephone lines or several hundred trunks or mixture thereof, sport their own processors, which perform most call handling processes, using their own memory boards. Originally the peripheral processors were to be Intel 8086, but those proved inadequate and the system was introduced with Motorola 68000 series processors. The name of the cabinet that houses this equipment was changed at the same time from Interface Module to Switching Module.

This distributed system lessens the load on the Central Administrative Module (AM) or main computer. AM is a dual processor mini main frame computer of the AT&T 3B series, running Unix. AM contains the hard drives and tape drives used to load and backup the central and peripheral processor software and translations. Disk drives were originally several 340 MByte SCSI multiplatter units in a separate frame, now a single multi-Gigabyte SCSI drive on a card. Tape drives were originally half inch reel to reel at about 6200 bits per inch, which were replaced in the early 1990s with 4 mm Digital Audio Tape cassettes.

T-carrier spans are terminated, one or two per card, in Digital Line Trunk Units (DLTU) which concentrate their DS0 channels into the TSI. Larger DS3 signals can also have their DS0 signals switched in Digital Network Unit SONET (DNUS) units, without demultiplexing them into DS1. SMs have Dual Link Interface (DLI) cards to connect them by multimode optical fibers to the Communications Modules for time divided switching to other SMs. Calls among the lines and trunks of a particular SM needn't go through CM, and a SM located remotely can act as distributed switching, administered from the central AM.

In contrast to Nortel's DMS-100 which uses individual line cards with a codec, most lines are on two stage analog space division concentrators or Line Units, which connect as many as 512 lines as needed to the 8 Channel cards that each contain 8 codecs, and to high level service circuits for ringing and testing. Both stages of concentration are included on the same grid board. Each grid board serves 32 lines, 16 A links and 32 B links. The Line Unit can have up to 16 grid boards connecting to the channel boards by shared B links, but in offices with heavier traffic for lines a lesser number of grid boards are equipped.

Since Line Units handle the high voltages and currents of analog lines, their cards fail at higher rates than ones that handle only computer voltages. Power for all circuitry is distributed as 130 VDC and converted to logic or telephone voltages as needed by DC/DC converters on each shelf of circuit packs.

Some lines, especially ISDN or PBX ones, are served by individual line cards.

[edit] Administration

The system is administered through an assortment of teletypewriter "Channels" (also called the system console) such as the TEST channel and Maintenance channel. Typically provisioning is done using a one of two methods - a command line interface (CLI) called RCV:APPTEXT, and through the menu-driven RCV:MENU,APPRC program. RCV stands for Recent Change/Verification. Most service orders, however, are admininstered through Recent Change Memory Administration Center (RCMAC).