Gradually opened in phases between 1994 and 1995, the Stagecoach Supertram serves the city of Sheffield with three light rail routes, covering a total of 29km. The Supertram plays a key part in the city’s infrastructure and half of the system is located on streets running with mixed traffic.

Memory tokens with a serial interface help the vehicles accurately navigate the streets. Orion Projects, which was responsible for the upgrade of the Supertram Vehicle Identification System (VIS) and tasked with upgrading the tram to track communication system, has been using Datakey Electronics’ Electrically Erasable Programmable Read-Only Memory (EEPROM) devices distributed by Nexus.

The VIS system manages the routes, signalling, stops and priority levels for the tram, helping it to integrate seamlessly with urban traffic. Accurate communications are essential for the efficient functioning of the tram, so a memory solution was needed that would provide flexibility, as well as safe and rugged data storage. To meet the demands, Datakey Electronics’ serial interface token was chosen to store configuration data, which is uploaded onto the token by the Orion team and then plugged in at trackside boxes.

The memory token will ultimately be used to store configuration data at 59 trackside locations. This data is used for controlling trackside traffic controller points and signals, and because each location is different, individual controls need to be used for each token employed.

A set of inductive loops are hidden underneath the tracks and act as a sensor for the tram, providing continuously updated status concerning tram location to the trackside equipment and the Operational Control Centre. The trackside hardware reads the information stored on the memory token and, based on the signals it receives from the loops, sets the appropriate output information. The tokens contain a variety of possible responses called up from data tables and the right option is chosen for individual locations.

“The tokens supplied by Nexus are used to determine the operation of relay outputs which help direct traffic controllers and trackside control equipment. Traffic controllers are located at every major junction and their aim is

to effectively control traffic lights and vehicle priorities. The data table stored on the token is used by the trackside equipment to signal the traffic controller so that trams get priority in mixed traffic, alongside cars and buses,” explained Roger Burridge, director at Orion Projects.

This technique allows a tram to cross the network of tracks in Sheffield and ensure it does so as quickly as possible.

Burridge said: “Having a token that you can literally plug and play has significantly streamlined tram communications. This means that when required, a new memory token can be programmed at headquarters and then a trackside engineer can just plug it in after removing the old one. Furthermore, the tokens are reliable and easy to reconfigure – they can be used time and time again.”

Reliable receptacles that help read the information uploaded onto the token are perhaps the most critical aspects of the system. Nexus offers a range of field-proven mating receptacles from Datakey Electronics’ for each data-carrier system.

Nexus distributes the full range of Datakey Electronics’ memory systems. They are available with SPI, I2C, Microwire, USB and

SD Interfaces. Memory capacities range from 1Kbit to 64GByte allowing easy customisation that fits particular application requirements. These products are ideally suited for data-logging, parameter and configuration upload, data storage and access control.

Nexus   T: 01794 301439