The primary function of the London Underground Station Computer
(SC) is to control
that make up the Automatic Fare Collection System
include the Automatic Gates, the Few Fare Machines, Multi Fare Machines and Queue Busting Machines.
Secondary functions of the SC includes providing monitoring for the station, communication with the Central Computer, distribution of fare tables to the equipment, consolidating revenue information and provide feedback from emergency systems.
The London Underground SC software was originally written for the Digital PDP 11/73 machine, but it has since been ported to VAX. The software runs on VAX and DEC Alpha computers.
The SC communicates with the station equipment through 9600-baud asynchronous multidrop serial lines. Each serial line supports 32 devices. The SC also has Station Control Units, which are normal PCs connected to the SC via an Ethernet connection.
All data is cached in the SC, and the SC keeps a copy of this data for a set period. This is in case the data is corrupted at the Central Computer or a communications failure occurs. Should the main Central Computer line break, the data can be sent manually via Portable Data Transfer Units.
The SC can provide the station managers with reports and management information, including volume of passengers, maintenance and station financial data.