Each NYC Metro subway station
has a Station Computer
(SC), which provides data communication
for all of the devices
in a station, including turnstile
s and token
The SC resides in the cabinet assembly at the end of a turnstile array. It is an IBM Intel 80406-based 7546 industrial computer. The SC is configured with an IBM Multiport Serial Adapter, an IBM Asynchronous Real-time Data Interface Co-Processor (ARCTIC Portmaster), an eight port serial communications adapter, an IBM DSU board and an uninterruptible power supply.
The SC communicates with all of the station devices through serial communications, which are routed through the Station Networking Module. The SC receives device status information, MetroCard and pass data, register data and maintenance and emergency alerts. All the information gets routed to the Area Controller, which acts like an area Central Computer. The SC retains data while it transmits it to the Area Controller. When the Area Controller has processed the information and stored it on two separate data backup systems, it sends an ACK message to the SC, which purges the now redundant data.
The SC controls the station equipment either through commands sent via the Area Controller or independently should ther be a communications outage. During periods of prolonged communications blackouts, data may be manually copied to the Area Controller. The communications link between the SC and the Area Controller includes a digital leased line, which is set up to act as an 8-point multidropped system. Each control area can have up to 24 turnstiles and three automated vendors.
The SC contains diagnostic software for maintenance. The maintenance system is based on a GUI interface.