Nov 05, 2008TagMaster, a Swedish manufacturer of RFID solutions for rail and transportation applications, has debuted a new tag designed for the metro, light-rail and mainline rail systems.
The S1470 CableTag is a heavy-duty, 2.45 GHz semi-passive tag that uses a proprietary air-interface protocol. But unlike the company's other semi-passive tags that can communicate only via a wireless RF signal, the CableTag can also be connected via a cable (using an RS485 serial communication interface) to external systems onboard a train, such as units that control the train's movements, or those that manage driver and route information. The CableTag can also be connected to track-side systems, such as signaling or traffic-management systems.
"CableTag utilizes the cable connection to allow its data memory to be dynamically updated by the external system it's connected to. It also receives its power source via the same cable," says Richard Holt, director of transportation at TagMaster, which is headquartered in Stockholm and was founded in 1994.
Most rail tags are used simply to identify the trains to which they are attached. But many firms would like to be able to transfer real-time information beyond a train's identification. Because the tag's programmable memory—which can store up to 574 bits of data—can be dynamically updated via the cable, more information can be passed to and from the train by communicating with an interrogator installed along the train tracks, or at a station. Onboard systems can communicate with the CableTag regarding new arrival times, for instance, and that information can then be passed from the CableTag to a track-side reader.
Conversely, the CableTag can be mounted along a track and the reader installed on a train, thus enabling a track-side system to share information with that train. For example, updated routing information from a traffic management system can be communicated to the track-mounted CableTag, and a train-mounted reader can capture that data as the train passes. The interrogator can then share that route information with the onboard system that manages such data.
The CableTag's ability to automatically capture information, then update onboard and track-side systems with that data, can replace the more manual-intensive processes currently in use. By automating these functions, the level of operational efficiency and reliability can thus be improved.
"By automating these functions, the level of operational efficiency and reliability can be improved," Holt says. "The CableTag enables this through its ability to be updated via its direct connection with onboard systems, and then that up-to-date information can be reliably sent to track-side systems via a reader placed on the track. In light-rail applications, it's common to [manually] send signal status or platform information to the driver to improve operational reliability. The CableTag can be connected to track-side systems and allow onboard readers to [automatically] update the driver."
According to Holt, the CableTag has been a design concept for several years, but has now finally been put into production because several customers have sought the functionality it provides. Although TagMaster's clients have requested anonymity, Holt says one of them is a train manufacturer. "In this application," he states, "the CableTag will be implemented in an onboard configuration, on one of the largest metro systems in the U.S.A. It will be used to automate an existing manual system in order to improve operational efficiency and increase the availability of train status information within the train control systems."
TagMaster offers two families of tags: the long-range (LR) series and the heavy-duty (HD) series. The LR tags are offered by the company's vehicle access business, which is focused on automatic vehicle identification (AVI) applications within parking and access control. The HD series, which includes the new CableTag, is offered through the transportation business and is focused on railway and industrial applications. Designed to meet specific requirements, the company indicates, the HD tags offer high reliability, rugged enclosure design and resilience to vibration.
All of TagMaster's HD tags are semi-passive, using a battery (or, in the CableTag's case, a cable) to power the tag's silicon chip. "This allows the tag to be continuously awake—i.e., always ready to respond to the RF signal sent by the reader—so the read time is very fast, up to 10 milliseconds," Holt explains. "We are able to maintain a very low output power in the reader, which doesn't need to power up the tag via the RF energy, as is the case for passive tags. This ensures that our RFID system is compliant with any national limitations on output power and can, therefore, be installed all over the world, without the need for any site licensing."
The tags' nonreplaceable batteries generally have a life span of 10 years, Holt says, and TagMaster's RFID technology creates a well-defined reading zone providing long read ranges (typically up to about 33 feet) at a passage speed of up to 248 miles per hour. The tags are identified by interrogators using a backscattering technique, in which the tag receives the signal from a reader, encodes it with data and reflects it back to the reader.
